Category: Smart cities
A network of sensors has been set up in Newcastle in order to give policymakers a more accurate picture of the air being breathed by children.
The project is a collaboration with Newcastle University and Newcastle City Council who have installed 22 air pollution sensors outside schools that are located close to major roads.
The data will be collected by Newcastle University’s Urban Observatory, the team will then use this information to help engage the children who are being directly affected and give them a voice as to how their cities should be planned in the future.
The Urban Observatory is the UK’s largest urban experiment collecting data about 60 different urban indicators, everything from energy use, rainfall and flooding to air pollution and traffic flow.
Currently, the Urban Observation has deployed over 3,600 sensors across Newcastle, including AQMesh air quality monitoring systems*, adding 5,000 new observations ever minute.
Eugene Milne, director of public health at Newcastle City Council said: ‘Poor air quality harms everybody’s health, and young people are among those most at risk, so we’re very pleased to be working with the University and young people across the city to address this.’
‘As well as raising awareness of the issues, the project will also aim to encourage more active travel and fewer car journeys, particularly on the school run.’
‘This project will help us to monitor just how much pollution is in the air around schools and enable us to get views of the children who are directly affected on what else could be done to tackle the problem.’
Sean Peacock, who is based in Newcastle University’s Open Lab has said: ‘Children themselves are far from oblivious to the impact that air pollution is having on their health and their futures.’
‘The school climate strike shows that young people are forcing air pollution and the climate crisis to the top of the political agenda.’
‘Urban planners and politicians are often hesitant to work with children, but they shouldn’t be.’
‘We need to embrace their creativity and passion to take radical action on air pollution and climate change. More, now than ever, we need the original ideas that only children can bring.’
All of the data is freely available at Newcastle University’s website: www.urbanobservatory.ac.uk, and is being used by researchers, local authorities, regulators, developers, town planners, businesses and members of the public.
*Original news published in September 2018.
Last month Environmental Defense Fund Europe (EDFE) together with Mayor Sadiq Khan are releasing the second wave of data from Breathe London, an ambitious collaborative project to measure and map air pollution across the capital.
In addition to nitrogen dioxide (NO2) measurements from the network’s 100+ stationary AQMesh pods, the interactive map now includes preliminary data from the Google Street view car drives as well as current and average pollution data for fine particulate matter (PM2.5).
The new data confirms a concerning trend: Air pollution across the capital remains dangerously high. Four out of every five pods, including 90% of schools in the network, are on track to exceed World Health Organisation (WHO) annual guidelines for PM2.5, which is linked to a wide range of adverse health effects. Additionally, preliminary analysis of the mobile data shows NO2 is on average over 50% higher on major through roads than quieter, local roads.
The findings corroborate what EDFE has been saying for some time: Bold action at the national level is needed to cut pollution and create healthy, breathable cities.
Small airborne particles like dust, soot and drops of liquids can create PM. Most PM pollution formed in urban areas is from fossil fuels used in vehicles, construction equipment, heat & power (including wood burning) and commercial cooking.
PM2.5 is made up of tiny particles, which penetrate deeper into the lungs and are linked to lung disease, heart attacks, strokes, asthma and cancer, as well as shorter life spans. This pollution is particularly dangerous for young people – studies show that PM₂.₅ exposure can impair childhood lung development.
Breathe London’s data from the stationary network suggests that over 80% of the pods are likely to surpass WHO long-term guideline for PM2.5. In other words, the annual average concentration of PM2.5 pollution – at the vast majority of measuring sites – is at unsafe levels.
Moreover, although thresholds for PM have been set as general guidelines, there is little evidence to suggest a safe threshold exists below which there are no adverse health effects. Despite the recognition that PM is not safe at any level, it is currently legal in the UK to have pollution levels above what is recommended by the WHO.
Since autumn 2018, two specially-equipped Google Street View cars have been driving London’s streets to measure air pollution. Data from the drives undertaken so far are now visible on the map.
When comparing pollution readings from busy versus quieter streets, preliminary analysis reveals NO2 is on average over 50% higher on busy major through roads than on quieter, local roads*. Like PM, pollution from NO2 is linked to a variety of health impacts, including aggravating asthma and adversely impacting lung function in children.
Amanda Billingsley, Managing Director of Environmental Instruments, the company that manufactured the AQMesh pods, said: “This is a great example of what can be shown by data from a network of stationary small sensor air quality stations, delivering insights that help government and citizens to take effective action to transform pollution exposure levels.
“We have supplied networks of these small monitors in various countries, but it is great to see the potential impact of hyperlocal data – enabling the assessment of air pollution on a street by street basis – in our own capital city.”
The Breathe London data will also be available on the new Air Quality Data Commons (AQDC), an open-access data platform where people can share and use data from low-and medium-cost air quality sensors.
*Comparison assumes error is random. Additional analysis will be conducted after mobile data collection concludes at the end of October 2019.
A version of this article ran on Environmental Defense Fund Europe’s blog on 22 Oct, 2019.
Whilst not the only AQMesh pods still in regular use since the product was commercially launched in 2013, two AQMesh pods are still in use in Spain and demonstrate the long life of this small sensor air quality monitoring system.
Over the last six years, the two pods have been loaned by AQMesh distributor in Spain, Envirodata, to a number of customers for trials and demonstrations, as well as being involved in a range of projects.
In one of these studies the pods were selected to determine how accurately small sensor systems could measure ambient levels of NO2. The collaborative research between the European Life Photoscaling Project, Tecnaire-CM, Greater Madrid Region and Madrid City Council sought to assess the effectiveness of different photocatalytic pavements in reducing levels of NO2 pollution. The AQMesh pods were co-located with two of the region’s larger air quality monitoring stations under traffic and urban background conditions to compare AQMesh readings with reference and calibrate field readings. A paper was published in August 2018 as a result of this study, which determined that with local calibration AQMesh meets the Air Quality Directive’s standards of accuracy at high concentrations of NO2.
These very first AQMesh pods have also been used to determine baseline air quality levels for the La Nucia project in Alicante, in anticipation of the development of a new sports facility. More recently, one pod has been used to evaluate levels of ozone (O3) during the hotter weather in an area within San Agustin, and the other is currently being used by the Madrid Regional Government. Previously, the municipality of Madrid used AQMesh to measure air pollution as part of a traffic reduction scheme, including to reduce speed limits and restrict access to downtown Madrid.
Luis Lombana of Envirodata comments “AQMesh technology is providing us with a unique solution to local air quality monitoring. The combination of compact hardware with advanced data processing algorithms makes AQMesh the best system for mapping city-wide pollution. We have been using these two AQMesh pods for demonstrations and projects since 2013. They have been upgraded by the manufacturer on a few occasions and we are pleased to be able to offer the best AQMesh performance to users with these two old friends. We have no plans to stop using them although we now also sell units with the additional options available, such as PM monitoring.”
The two pods were initially built to measure NO, NO2, O3, CO and SO2, powered by an internal lithium battery, which powers a ‘gas only’ pod for over two years. From 2015 the pod was able to take advantage of developments in the electrochemical sensors, particularly factory sensor characterisation introduced in 2015 (v4.0) and the ozone filter introduced to the NO2 sensor in 2016, which dramatically improved discrimination of O3 and NO2, particularly with the AQMesh proprietary data processing algorithm v4.2. The pods will now be upgraded remotely (a setting change on the AQMesh server), with full traceability, to v5.1 which offers significant improvements in accuracy at higher temperatures.
As well as the original 5-gas suite of sensors, AQMesh can now offer two additional gases – H2S and CO2 – as well as particulate matter (PM1, PM2.5 and PM10), plus noise, wind speed and direction. Other power sources are available with solar being the most popular.
AQMesh pods have been operating in the field since 2013, and so far have been active in over 60 countries in a range of air quality applications. The pods have always been built to a rugged and robust standard, with hundreds of pods installed for years in city centres around the world. The inconspicuous units generally avoid vandalism, damage or malfunction, and in one instance a customer’s pod has still continued to function and transmit data despite being crushed during an accident. They have also proven to withstand extreme weather conditions, continuing to work under several feet of snow during the North American winter and the hot desert climates in the summer months in Australia, South Africa and the Middle East.
A study published in the Journal of the American Medical Association has found that long-term exposure to poor air quality can have the same damaging effect as smoking 20 cigarettes a day, with air pollution shown to be more dangerous than passive smoking.
Many employees are exposed to poor air quality on a regular basis and employers are often unaware of the risks and what they can do to manage them. A new generation of air quality monitoring equipment is now available for measuring the levels of common air pollutants in the immediate areas where staff are working.
Employees working close to areas of high road traffic, particularly with poor air circulation, are especially vulnerable to the effects of pollution. As well as being trapped indoors or brought in through ventilation systems, pollutants can also build up in outdoor spaces, particularly in cities with high buildings, leading to exposure levels which may exceed limits set by the World Health Organisation (WHO).
Diesel fumes were classified as a Class 1 Carcinogen by the WHO in 2017, after it found that people exposed to diesel fumes at work were up to 40% more likely to develop cancer. As such, employers can now be sued if their employees develop cancer later in life as a result of exposure, as reported by The Sunday Times following the reclassification.
The EU limits for nitrogen dioxide (NO2) exposure are 40µg/m3 annually and 200µg/m3 in an hour, no more than 18 times in a year. Many official measurement stations in cities worldwide report NO2 above the annual limit but less is known about local levels of this pollutant. Because NO2 is produced as a direct result of a source, such as traffic exhaust or diesel generators, levels of NO2 regularly exceed the hourly limit when measured in ‘hotspots’, such as busy road junctions, where it is not practical to install a large air quality measurement station, or on a private site.
Previously, air quality has been likened to passive smoking. The International Agency for Research on Cancer (IARC) determined in 2013 that air pollution is more dangerous than passive smoking, and was now the leading cause of cancer. At the time, the IARC’s Kurt Straif told the South China Morning Post “The air we breathe has become polluted with a mixture of cancer-causing substances. We consider this to be the most important environmental carcinogen, more so than passive smoking.”
Measuring ozone (O3) as a part of an air quality monitoring routine is also becoming increasingly important, especially in hotter climates and areas of increased VOC emissions. O3 at ground level is dangerous and is formed by reactions with nitrogen oxides (NOx) and volatile organic compounds (VOCs) from traffic and industrial emissions in the presence of sunlight. This means hotter, sunnier weather can dramatically increase O3 pollution in urban and industrial areas. The WHO currently states the daily limit of O3 levels to be 100μg/m3 over an 8-hour mean and advise that prolonged exposure to high levels of O3 can have severe effects on human health. These include asthma, inflammation of the airways and reduced lung functionality, just as the recent studies comparing air quality to smoking has found.
Senior co-author of the study Dr Joel Kaufman, from the University of Washington, said: “We were surprised to see how strong air pollution’s impact was on the progression of emphysema on lung scans, in the same league as the effects of cigarette smoking, which is by far the best-known cause of emphysema.” The professor of environmental and occupational health sciences and epidemiology added: “We really need to understand what’s causing chronic lung disease, and it appears that air pollution exposures that are common and hard to avoid might be a major contributor.”
Teams responsible for protecting staff from exposure to hazards can now understand exposure in relevant locations by installing compact air quality monitoring equipment designed to continuously measure pollution levels in ambient air.
AQMesh pods are small, wireless units which can be mounted on a lamp post, fencing, wall or a similar mounting point close to where staff are breathing potentially polluted air, both indoors and outdoors. Air quality readings are secure and confidential, accessed online by authorised personnel only.
AQMesh has been used on building sites, industrial sites and at roadside locations worldwide, as well as measuring the air intake into office buildings, in order to monitor the air quality of employees working in these areas on a daily basis and helping to protect them.
Minnesota Pollution Control Agency (MPCA) has been monitoring Minnesota’s air quality for a number of years, and it is generally considered to be good. However, MPCA wanted to understand how air pollution varies across small distances in order to minimise vulnerable communities’ exposure to harmful pollutants.
Following project funding* in 2017, earlier this year MPCA successfully installed AQMesh pods across 44 sites in neighbourhoods around Minneapolis and St. Paul, primarily on lampposts in school parking lots, with at least one pod in each ZIP code.
MPCA gives high priority to community involvement and sharing its air quality data with the public. It has launched an online tool allowing citizens to compare pollution levels at different monitoring sites over a given date range. Monika Vadali, Ph.D, who is leading the project, welcomes feedback on the online tool and the wider project and is looking forward to hearing comments from communities where monitoring is taking place.
Prior to being deployed across Minneapolis and St. Paul, the AQMesh pods were co-located against the FEM station at Blaine airport for a number of months in order for the readings to be compared and validated, and for scaling to be applied if necessary. During the co-location period AQMesh showed high levels of pod-to-pod precision, with an average R2 of 0.94 for NO2, despite extreme weather conditions.
For the next two years, the AQMesh pods will monitor and report data on levels of NO2, O3, NO, SO2, CO, PM2.5 and PM10 in 44 areas of Minneapolis and St. Paul to build up a picture of air quality across the cities. Scientists at MPCA will use the data to determine if there are any significant differences in the concentration of pollutants between ZIP codes, if there are any areas with unusually high levels of pollution, and if technology such as AQMesh is suitable for measuring such small variations in air quality.
The study is similar to the Breathe London project in the UK, where 100 AQMesh pods have been deployed across London to publish a real-time map of the city’s air pollution, which has now also been launched online.
For more information about the MPCA project, please contact Monika on (+1) 651-757-2776.
*This is a legislative funded LCCMR project, with support provided by the Environment and natural resources trust fund (Subd. 07 Air Quality, Climate Change, and Renewable Energy ENRTF # 07b).
Partners and collaborators include the city of Minneapolis, the city of St. Paul, Minnesota Department of Health, Minnesota State University-Mankato, and Xcel Energy.
Detailed information on London’s (UK) air pollution is now being published on breathelondon.org, the website for a new collaborative project to paint a clearer picture of the city’s air quality. The readings are being provided by a network of AQMesh air quality monitoring pods supplied and installed by Air Monitors, part of the ACOEM Group.
The AQMesh pods are stationary – mostly mounted discreetly on lamp posts, but the pod data is being supplemented by measurements from instruments that have been installed by Air Monitors in two Google Street View Cars, as they travel the city’s streets.
Visitors to the Breathe London website will be able to view almost live data (within an hour) on nitrogen dioxide (NO2); one of the urban pollutants of greatest concern.
“This is a major step forward,” says Felicity Sharp, Air Monitors Managing Director. “The availability of highly localised air quality data is critical to the empowerment of citizens so that they can make choices that affect the quality of the air they breathe.
“In the past, air quality data has not been sufficiently local to allow most citizens to change the way they live their lives, but with the benefit of this website they will be able to choose where they want to walk, run, play, go to school or even buy a house.
“The data will also help to raise awareness and thereby encourage citizens to choose more environmentally friendly transport modes, particularly in pollution hotspots.
“Importantly, the data will also help national and local government to assess the effectiveness of air quality improvement measures. So this is great news for London, and we hope that it will be replicated in similar smart city projects around the world.”
Schools near Glasgow have been monitoring air quality as part of a project aiming to reduce the levels of pollution emitted by vehicles as they drop off and collect children. The project is part of a ‘Beat the Street’ initiative that was granted £50,000 from a new £1million fund to increase walking, cycling and sustainable travel in Scotland. The overall aim is to cut Scotland’s carbon emissions, improve air quality, reverse the trend towards sedentary lifestyles and tackle health inequalities.
The Environmental Health department of East Renfrewshire Council supplied and installed the three AQMesh air quality monitoring pods that were utilised in the project. The monitoring activity followed initiatives in eight schools organised with SEPA, in which the children designed their own air quality banners as part of a competition.
The banners were then placed outside the schools which were then monitored for two weeks with an AQMesh pod measuring a variety of parameters including nitrogen dioxide – one of the pollutants of greatest concern. The Council’s Richard Mowat said: “We used one of our own AQMesh pods and rented the other two from Air Monitors. The pods are small and easy to install so we were able to locate them close to the areas most affected by parents’ vehicles.
“The results clearly showed significant peaks in pollution during the drop-off periods and it was pleasing to note how well the project was received. We hope that this work will help educate the children and that they, in turn, will encourage their parents to leave the cars at home and walk whenever possible.”
Anne-Marie Absolom is Head Teacher at one of the participating schools – St Clares Primary School. She said: “Our Junior Road Safety Officers, and all of the school staff, are delighted that we have had the opportunity to install temporary air quality monitors in our car park.
“We have been campaigning throughout the year to improve air quality in and around our school. The children have also been learning about the small changes that they can make – changes that will make a big difference to the quality of the air we breathe.
“The results from the monitors have highlighted the specific times of day at which air pollution is most significant, and the Junior Road Safety Officers are now campaigning at these times. The data gathered has been shared with all children in the school and they are passionate about spreading the word and ensuring that air pollution is reduced.”
As well as supplying the monitoring equipment for the project, Air Monitors also provided sponsorship funds for the school banners, and this was reflected in a stunning night-time time display on the roof of Glasgow’s famous SEC Armadillo, organised by SEPA. A variety of images relating to air quality were projected on to the Armadillo’s roof, highlighting for example Clean Air Day 2019, as well as the Air Monitors logo.
SEPA’s Dr Colin Gillespie said: “It has been great to work again with Air Monitors and the councils, raising awareness in air quality around schools, promoting active changes to reduce pollution and encouraging pupils to think about more sustainable forms of travel.”
Following a successful evaluation phase in 2018, AQMesh small sensor air quality monitoring ‘pods’ have been selected for use in a project to control the ventilation of a road tunnel in the city of Marseille.
Supported by the AtmoSud (AirPACA) local air quality monitoring network, the CETU (Tunnel Studies Centre) and AQMesh distributor Addair, eight AQMesh pods were installed in February 2019, monitoring nitrogen oxides NO and NO2, in an innovative experiment in one of the covered sections of the L2 ring road in Marseille. Called “Boreas project”, after legendary ‘dispersing’ winds, this study aims to use pollution measurements near tunnel entrances to activate in-tunnel fans.
Urban planning is increasingly routing vehicles underground. Although this approach eases air quality and noise at some locations – and overall reduces the level of pollution the population is exposed to – there is a risk that residents living close to the tunnel heads are actually exposed to higher concentrations of pollution as air is expelled from the tunnel.
The L2 ring road in Marseille consists of a succession of covered tunnels over 12Km in dense urban areas. The phased project at the Montolivet South tunnel heads will implement a system for the conditional triggering of in-tunnel fans to evaluate its impact on air quality in the zones adjacent to the nearest residents. This approach was tested in 2018, with micro-sensor readings compared at the AirPACA Kaddouze monitoring station. A first phase analyses the pollution without activation of the ventilation system, then a second phase with ventilation.
The aim is to determine the link between ventilation and dispersion of the pollution at the end of the tunnel and to determine the most effective protocol for activation of the ventilation systems based on real-time air quality levels, inside and outside the tunnel. Automated alerts for high NO2 levels are already in place. The feasibility of this approach will also be reviewed by analysing efficiency in terms of cost and energy consumption. In theory, the use of ventilation could improve the quality of air at the head of the tunnel. However, in some weather conditions this could simply displace the pollution and this forms part of the study – analysing the pollution concentration and dispersion in different meteorological and traffic conditions.
AQMesh has been used in other tunnel monitoring projects, including several in the UK, specifically to study ventilation efficiency in road tunnels where pollution can build up if sufficient air flow is not maintained. During the UK projects, AQMesh pods were also first co-located with a nearby reference station to ensure measurements were directly comparable.
The pods were then deployed at different positions within the tunnels and in ventilation ducts, studying how the concentration of pollution changed when air flows were adjusted in varying traffic scenarios. The pods were able to run for up to six months without any maintenance or calibration, despite the very high pollution levels recorded. The results obtained in these studies enabled optimisation of the ventilation settings and helped to reduce energy consumption whilst maintaining cleaner air for tunnel users and maintenance personnel.
Supporting the aims of Clean Air Day today, 20th June 2019, the Guardian has published a short film demonstrating the changing levels of pollution that children are exposed to as they walk to school in London. The film can be viewed here.
The Guardian Cities team worked closely with their colleagues in multimedia to create a film showing real-time air quality data as a mother takes her young children to school in north London. The video features mother-of-two Natasa pushing a pram and walking her daughter along Marylebone Road, with a Particles Plus instrument attached to the pram and an AQMesh pod on her daughter’s backpack.
The most important air quality parameters are displayed on-screen during the walk, with data including PM10, PM2.5 and nitrogen dioxide (NO2). The film producers have cleverly integrated the European yearly mean limits for these parameters into the display, with readings changing from blue to red when they exceed the limit, (which for PM10 and NO2 was most of the time!).
Documentary producer Anetta Jones, said: “Air quality is a vitally important issue for the health and wellbeing of city dwellers, but the main pollution threats are invisible, so we hope that initiatives such as this will help residents and visitors to better understand the threat that they face.”
The monitoring equipment was supplied by Air Monitors Limited. Their David Green said: “We have recently installed large numbers of AQMesh pods all over London as part of the Breathe London project, and data from these pods will be displayed on the project website. However, video is an enormously popular medium, and it is really exciting to see what can be achieved when the latest technologies in multimedia and air quality monitoring combine.”
A new network of air pollution monitors has been installed to record emissions from cruise ships docking in Greenwich.
The £80,000 network has been funded by the Port of London Authority (PLA) and installed in partnership with Breathe London and the borough councils covering both Greenwich and Tower Hamlets.
The eight monitoring stations, all located close to the Greenwich Ship Tier landing stage, will capture data around the clock with the raw data available via the websites of both the PLA and Breathe London. A full analysis of the results will be published in early 2020.
The monitors have been supplied by Gloucestershire-based Air Monitors Limited.
Robin Mortimer, PLA chief executive said: ‘The data these monitors collect will give us a comprehensive understanding of the impact that the cruise ships have on air quality when they are in town.
‘It’s crucial to have this information so that we can address the concerns that we know are very strongly held by local residents.’
The monitors are part of the PLA’s Air Quality Strategy, published in May 2018, the first to be produced by a UK port. It includes 25-year targets to halve levels of Nitrogen Oxides and Particular Matter from river-related sources, whilst growing use of the river for carrying both freight and passengers.
Measures already implemented include a programme of retrofitting older vessels with the latest environmentally-friendly technology.
In January, the Department for Transport (DfT) published the first-ever maritime strategy, which details their vision of a zero-emission shipping industry by 2050.
In it, the government said they are considering introducing targets to drive down emissions of GHGs and other air pollutants from UK shipping as ‘the volume of global trade increases.’
They also say they hope to have a group of hydrogen or ammonia powered domestic vessels in operation and at least one major ‘smart port’ in the UK to have all ship-side activity zero emission (including non-road mobile machinery like cranes).
Few people know how clean the air is where they live, work, exercise or where their children go to school. Although air quality can be shown to vary significantly over short distances, air pollution is generally measured using a small number of large, expensive and high quality monitoring stations. The equipment used in these stations is very accurate and complies with measurement standards but they are expensive to buy and maintain, as well as difficult to position because of their size and infrastructure requirements.
With most cities having a single figure number of reference stations at best, many neighbourhoods do not have access to regular and localised air quality information. Historically, the best solution currently is to fill the gaps through modelling, which combines available air quality readings with other information such as emissions inventory.
Demand from communities for better local air quality information is coming at a time when development of smaller, cheaper air quality sensors can provide a solution to the challenge. ‘Small sensor’ air quality systems can provide highly localised pollution measurements, including nitrogen dioxide (NO2) and the key particulate matter measurement, PM2.5, but to provide meaningful measurements on which communities and authorities can make decisions, the information must show traceability to reference measurements.
Many initiatives around the world are aiming to show what can be done, with one of the most ambitious being the Breathe London project in London. 100 small sensor systems are being used, in combination with data from London’s reference network, modelling and readings taken by Google cars modified to carry high quality air monitoring equipment. This project aims to demonstrate how such a ‘hyper-local’ network can be managed, creating a template which can be rolled out to other cities worldwide.
Similarly, 50 AQMesh small sensor air quality monitoring units have been installed to monitor air quality in each of the 50 zip codes in Minneapolis – Saint Paul, USA. “This project is about understanding small-scale differences in air pollution in urban areas in order to minimise exposure to harmful air pollutants, particularly for vulnerable communities. The Assessing Urban Air Quality project will use new air monitoring sensors to broaden our knowledge about air quality in Minneapolis and St. Paul”, commented Monika Vadali, Ph.D, who is leading the project.
AQMesh has also been used to monitor air quality around industrial sites and next to nearby communities which may be affected. As the monitoring units can be positioned with a high degree of flexibility, such as mounting on a lamp post, it is possible to capture data at exactly the point required. With measurements usually every 15 minutes, combined with local wind speed and direction information, it is possible to build up a highly localised picture of likely pollution exposure and identification of pollution sources.
Whilst regulatory authorities are currently defining testing methodologies to help users choose small sensor air quality systems, the best small sensor systems provide a useful and practical tool to supplement existing monitoring networks and are in active use around the world, providing new information about local air quality for a range of applications.
North Americans will be well aware of the particularly harsh weather in the early months of 2019, but AQMesh has taken conditions in its stride. The AQMesh stated operating range of -20°C to + 40°C is backed up by long-term operation across a wide range of climates.
AQMesh pods used by Minnesota Pollution Control Agency (MPCA) to measure pollutant gases and particulate matter, such as NO2 and PM2.5 , installed on streetlights around Minneapolis St. Paul have seen temperatures as low as -25.4°C (-13.7°F) and continue to run smoothly.
Monika Vadali, leading the MPCA project, commented “We are quite impressed with the temperatures we have seen this winter”. However, when asked for a photo of the pods, she said “I can’t get to any of the pods as we have had so much snow and cold that there is 5-6ft of snow around some of the poles, making access difficult.” Temperatures recorded elsewhere have not been so low this year but AQMesh pods have been installed over previous winter in Sweden, Finland, Canada and central Europe, with temperatures regularly dropping below -20°C.
Despite such harsh weather conditions, the AQMesh pods have continued to monitor and communicate data to the AQMesh server, where it is securely accessed by users. The hardware design has been refined to ensure the equipment has the resilience to survive, with minimal maintenance, for years. The initial concept was for the pod to measure pollutant gases, particularly NO2, for two years on a single lithium battery. Although many users now run shorter projects or choose solar or DC power sources, the principle – and challenge – is unchanged.
In addition to its physical design, data processing on the AQMesh server includes carefully developed correction algorithms which compensate for extreme conditions. Remote diagnostics also identify unexpected patterns in sensor output, which may affect confidence in the data, which is then flagged.
At the same time as the AQMesh pods were under several feet of snow in Minnesota, pods in the southern hemisphere have been regularly operating at temperatures in excess of 30°C, hitting 44.7°C in South Africa and 46.2°C in Australia.
AQMesh pods have been deployed long-term (many pods are in their sixth year of deployment around the world) and as temperatures rise across some of the hottest locations where pods are deployed – Kurdistan, Pakistan, Myanmar, Arizona (USA), Ghana – the latest generation of sensors and processing algorithm will continue to provide reliable and traceable air quality measurements in locations where other monitoring equipment cannot readily be deployed.
In the southern regions of the USA, with very hot temperatures and varying levels of humidity, AQMesh pods maintained high precision and accuracy against co-located certified reference equipment, with a correlation R2 of 0.92 for ozone, compared to collated FEM. Many parts of the world where AQMesh operates record relative humidity (RH%) over 90%, often on a regular or sustained basis.
AQMesh also stands up to high winds and extreme rainfall and is now available with an optional wind speed and direction sensor to complement its extensive range of measurable parameters. The meteorological data gathered by this sensor can help distinguish between local and regional sources of pollution.
In an inter-connected world, air quality is increasingly becoming another measurement made available to the public, but how reliable is the data?
Common air pollutants such as NO2 and PM2.5 mix at different rates depending on their source and local weather conditions, particularly wind speed, leaving large local variations in pollution levels. Urban air quality has traditionally been managed by authorities using a combination of large, compliance standard (reference) measurement stations and modelling based on an emissions inventory. Research has shown that increasing the number of measurement points improves the spatial resolution of urban air quality models.
Small-sensor air quality monitoring technology offers the possibility of more local measurements, and its emergence coincides with the appetite from Internet of Things (IoT) developers to map air quality across cities in real-time and communicate this information to the city inhabitants in various ways. This is leading to a growing number of smart city projects using a range of monitoring devices, but understanding the air quality information gathered and sharing it with the public can still be complicated.
Many air quality sensors that are small, cheap and have low power consumption are often very limited by the influence of fluctuating temperatures and cross-gas effects and do not produce good air quality readings. It is therefore beneficial to use a small-sensor air quality monitoring system that incorporates processing, correction and a QA/QC process in order to offer meaningful readings. Environmental authorities, including the US EPA, have developed air quality indices (AQI) and other tools to communicate local air quality to the public. These authorities are looking at how to modify that approach to provide more localised information from small sensor-sensor systems, such as air quality in a neighbourhood – or even a street – rather than a whole section of a city.
AQMesh, a small-sensor air quality monitoring system, is being used in a variety of successful smart city projects which have a range of objectives, but with a common goal of informing the public about the air quality and pollution levels in the local area where they live and work.
‘Breathe London’ was launched in February, with a sophisticated network of air quality monitors to help investigate and improve London’s toxic air. A range of fixed and mobile sensors will be used to build up a real-time, hyperlocal image of London’s air quality. The technology company Air Monitors designed and installed the network of AQMesh air quality monitoring pods, as well as the air quality analysers that were specially adapted to operate inside Google Street View cars.
In Minneapolis, Minnesota Pollution Control Agency (MPCA) has deployed 50 AQMesh pods across 50 zip code areas in order improve understanding of the small-scale differences in air pollution within urban areas.
Similarly in Newcastle, 55 AQMesh pods, supplied and supported by Air Monitors, form part of a network of over 600 sensors managed by the UK’s first Urban Observatory, which aims to provide Newcastle’s citizens with a digital view of how cities work.
These smart cities demonstrate that meaningful and reliable air quality information can be shared with the public when networks are deployed effectively and supported by air quality professionals who understand the capabilities – and limitations – of small-sensor technology and how the local environment affects air quality readings.
The UK’s first Urban Observatory, led by Newcastle University, has been designed to provide a digital view of how cities work. AQMesh air quality monitoring equipment is being deployed across Newcastle and Gateshead in conjunction with other instruments for monitoring parameters such as air and water quality, noise, weather, energy use, traffic and even tweets.
Forming part of a network of over 600 sensors, the Urban Observatory has already collected over half a billion data points and the information is now starting to shed light on the way different systems interact across the city and provide a baseline against which future cities can be developed and managed.
To date Air Monitors, UK AQMesh distributor, has supplied 55 AQMesh pods and 6 conventional air quality monitoring stations. The conventional stations employ standard reference method instruments to measure key air quality parameters such as Nitrogen Dioxide, Ozone, Carbon Monoxide and Particulates. The AQMesh pods monitor similar parameters, but are smaller, solar-powered, wireless, web-enabled devices that can be quickly and easily located in almost any location.
Commenting on Air Monitors’ involvement in the Urban Observatory project, Managing Director Jim Mills says: “The conventional stations are delivering precise, accurate data, and the AQMesh pods are providing the portability and flexibility to monitor air quality accurately and reliably in the locations of greatest interest.”
“Perhaps the most interesting aspect of this project is its ability to engage with the community, providing detailed local air quality data so that both authorities and citizens can make informed decisions on how to reduce exposure to air pollution. Looking forward, it is clear that work in Newcastle will serve as a model for other cities around the world to follow.”
The National Observatories facility was established in 2017 with the Newcastle Urban Observatory as the founding member, supported by £8.5 million investment from EPSRC (Engineering and Physical Sciences Research Council). The guiding principles are to be technology agnostic and vendor non-exclusive, open by default and transparent by design whilst developing a valued, long-term, sustainable platform. In order for the data to be useful to better understand cities and to facilitate evidence based decision-making across a range of scales and sectors, the data needs to be robust and reliable with known data quality that can be validated.
The AQMesh pods are also being used as part of the ‘Sense My Street’ tool box which enables local communities to deploy sensors and locate them on the streets, collecting evidence to inform or even change their communities.
Phil James, who co-leads the Urban Observatory research, explains: “Cities are complex environments and if we want to develop them sustainably we have to understand how everything interacts.
“By compiling observations and comparing the data, for the first time we are now able to make more informed decisions about designing our cities to work better for people and the environment. Through the Sense my Street project, we are able to give communities the power to gather data relevant to issues that are important to them at a very local scale.”
All of the data is freely available at Newcastle University’s website: www.urbanobservatory.ac.uk, and is being used by researchers, local authorities, regulators, developers, town planners, businesses and members of the public.
AQMesh has been measuring ozone (O3) using small sensors since 2011 and the readings from the latest generation electrochemical sensor, using AQMesh v4.2.3 processing, as compared to co-located certified reference readings, consistently show an R2 of over 0.9 with an accuracy ±10ppb (20µg/m3).
AQMesh pods have been measuring ozone levels around the world and co-location comparison studies show very good performance against reference equipment from the latest sensor and processing version. Ozone levels have been particularly high across Western Europe over this summer but are a regular concern in many parts of the world, including the USA. However, there are huge gaps between O3 monitoring points, to different degrees across the world, depending on monitoring equipment budgets. A lower cost small-sensor monitoring solution can provide valuable data within the areas currently lacking in this air quality information. Data validity is typically demonstrated by comparison with a local reference station, although AQMesh is also widely used where no reference data is available.
O3 at ground level is formed by reactions with nitrogen oxides (NOx) and volatile organic compounds (VOCs) from traffic and industrial emissions in the presence of sunlight. As such, hotter, sunnier weather can dramatically increase O3 pollution.
The World Health Organisation (WHO) currently states the daily limit of O3 levels to be 100μg/m3 over an 8-hour mean and advise that prolonged exposure to high levels of O3 can have severe effects on human health, including causing asthma, inflammation of the airways, reduced lung functionality and lung disease. Measuring O3 as a part of an air quality monitoring routine is therefore becoming increasingly important, especially in hotter climates and areas of increased VOC emissions.
O3 can be complicated to measure due to its high sensitivity to environmental conditions and cross-gas effects. Most small sensors for measuring O3 are either electrochemical or metal oxide, but electrochemical sensors (such as those used in AQMesh) have the advantage of low power requirements and can therefore be installed more flexibly. AQMesh pods are compact, wireless units and are available with a variety of power options, including solar panels, which allow them to be installed exactly where monitoring needs to take place.
During summer 2018 AQMesh has been measuring ozone at hundreds of locations across five continents and co-location comparisons show consistently high levels of accuracy. To quote two of many such studies, in an industrial region of the USA, AQMesh O3 measurements compared to FEM gave an R2 of 0.97, and in a similar comparison study in Western Europe the R2 value for O3 was 0.95. AQMesh pods measuring gases can run continuously for over two years using a battery but other power options are available, including solar. Particulate matter (TPC, PM1, PM2.5, PM10) can also monitored with an AQMesh pod, alongside gases including NO, NO2, O3, CO, SO2, CO2 and H2S, as well as pod temperature, RH% and pressure.
The accuracy of AQMesh readings has been proven through an extensive series of global co-location comparison trials and is the proven, commercially available low-cost air quality monitoring system for both pollutant gases and particulate matter, as well as simultaneously monitoring a range of environmental conditions.
London Mayor Sadiq Khan has launched a new, street-by-street monitoring system that will help to improve that capital’s air quality. From July 2018, and operating for a year, London will benefit from what is being described as the world’s most sophisticated air quality monitoring system. A consortium involving academia, an environmental charity, and commercial partners will install a network of 100 multiparameter AQMesh air quality monitors, whilst also operating two Google Street View cars that will map air pollution at an unprecedented level of detail.
Air Monitors Ltd will supply the AQMesh pods and manage data from all the sensor systems, so that air quality can be visualised and mapped in almost real-time. Working closely with the Greater London Authority, the project will be run by a team of air quality experts led by the charity Environmental Defense Fund Europe, in partnership with Air Monitors Ltd., Google Earth Outreach, Cambridge Environmental Research Consultants, University of Cambridge, National Physical Laboratory, King’s College London and the Environmental Defense Fund team in the United States.
Air Monitors Managing Director Jim Mills says: “It is difficult to underestimate the importance of this project – traditional monitoring networks provide essential information to check compliance against air quality standards, but this network will be ‘hyperlocal’ by which we mean that it will deliver street-level air quality data, which will be of tremendous interest to the public and also enable the effective assessment of air quality interventions.
“The Google Street View cars will take readings every 30 meters, helping us to find pollution hot-spots, so that AQMesh pods can be positioned in these locations. However, the pods are wireless and independently powered, so they can also be quickly and easily fixed to lamp posts in other sensitive locations such as schools.”
In addition to nitrogen dioxide and particulates, which are the pollutants of greatest concern, the pods will also measure ozone, nitric oxide, carbon dioxide, temperature, humidity and pressure. Data will sent, near real-time, to Air Monitors’ cloud-based data management system, which can be accessed by PC, tablet or smartphone by authorised partners, using an assigned login.
The monitoring data will provide baseline air quality data that will be essential in the assessment of mitigation measures, particularly in London’s expanding ultra-low emission zone. For example, on 20th June 2018, Sadiq Khan, announced the creation of the largest double-decker electric bus fleet in Europe, and the new monitoring network will enable the assessment of this initiative’s impact on air quality.
“This project will provide a step change in data collection and analysis that will enable London to evaluate the impact of both air quality and climate change policies and develop responsive interventions,” said Executive Director for Environmental Defense Fund Europe, Baroness Bryony Worthington. “A clear output of the project will be a revolutionary air monitoring model and intervention approach that can be replicated cost-effectively across other UK cities and globally, with a focus on C40 cities.”
Mark Watts, C40, Executive Director said: “Almost every major city in the world is dealing with the threat of toxic air pollution, which is taking an incredible toll on the health of citizens, public finances, quality of life and contributing to climate change. London is already a world leader in responding to this global threat and with this initiative it will set a new global standard for how street level air quality monitoring can inform strategic policy making. Cities across the C40 network and around the world will be watching closely to understand how this monitoring can deliver cleaner air for their citizens.”
About Environmental Defense Fund
Environmental Defense Fund Europe is a registered charity (1164661) in England and Wales. A recently established affiliate of leading international non-profit Environmental Defense Fund (EDF), the organisation links science, economics, law, and innovative private-sector partnerships to create transformational solutions to the most serious environmental problems. Connect with us at edf.org/europe, on Twitter and on our EDF Voices, EDF+Business and Energy Exchange blogs.
About Air Monitors Limited
Air Monitors is the UK’s leading air quality monitoring company, supplying and supporting instrumentation to central government, local authorities, research and industry. Air Monitors supplies and supports AQMesh in the UK and will also provide and maintain the equipment within the Google Street View cars in the project.
AQMesh is a fully developed and independently evaluated small sensor outdoor air quality monitoring system, manufactured in the UK by Environmental Instruments Ltd. and in use worldwide since 2012.
About Cambridge Environmental Research Consultants
Cambridge Environmental Research Consultants (CERC) are world leading developers of air quality modelling software. Their renowned ADMS-Urban model will be used together with the sensor data to generate hyper-local air quality mapping both for nowcasts and forecasts, and for policy studies.
About Google Earth Outreach
Google Earth Outreach is a program from Google designed specifically to help non-profit and public benefit organisations around the world leverage the power of Google Maps and Cloud technology to help address the world’s most pressing social and environmental problems.
About the National Physical Laboratory (NPL)
NPL is the UK’s National Measurement Institute, providing the measurement capability that underpins the UK’s prosperity and quality of life. Every day our science, engineering and technology makes a difference to some of the biggest national and international challenges, including addressing air quality issues. http://www.npl.co.uk/about/what-is-npl/
About University of Cambridge Department of Chemistry
The University of Cambridge Department of Chemistry is a world leading research and teaching institution. At Cambridge, the Centre for Atmospheric Science has played a primary role in the development of low-cost sensors for air quality monitoring and in the development of techniques for analysing and interpreting measurements from sensor networks.
About the C40 Cities Climate Leadership Group
Around the world, C40 Cities connects 96 of the world’s greatest cities to take bold climate action, leading the way towards a healthier and more sustainable future. Representing 700+ million citizens and one quarter of the global economy, mayors of the C40 cities are committed to delivering on the most ambitious goals of the Paris Agreement at the local level, as well as to cleaning the air we breathe. The current chair of C40 is Mayor of Paris Anne Hidalgo; and three-term Mayor of New York City Michael R. Bloomberg serves as President of the Board. C40’s work is made possible by our three strategic funders: Bloomberg Philanthropies, Children’s Investment Fund Foundation (CIFF), and Realdania.
Minnesota Pollution Control Agency (MPCA) has purchased fifty AQMesh pods to measure key air pollution gases and particulate matter across fifty different zip code areas. These small sensor air quality monitoring systems measure NO, NO2, O3, CO, SO2, PM1, PM2.5, PM10, temperature, pressure and relative humidity and will be installed – one per zip code – around the twin cities of Minneapolis and Saint Paul. The two-year project, funded by a legislative grant*, is to supplement the air quality information available to the public.
Deployment across the 50 zip codes has been mapped out after several public meetings involving the local community to determine where residents felt monitoring was needed. The small yellow triangles represent the points which local residents asked for sensors to be installed, and the green dots indicate the planned installation site based on the infrastructure available for mounting the AQMesh pods.
“This project is about understanding small-scale differences in air pollution in urban areas in order to minimise exposure to harmful air pollutants, particularly for vulnerable communities. The Assessing Urban Air Quality project will use new air monitoring sensors to broaden our knowledge about air quality in Minneapolis and St. Paul”, commented Monika Vadali, Ph.D, who is leading the project.
The pods are currently installed at the Blaine airport Federal Equivalent Method (FEM) station so that AQMesh readings can be compared to and validated against air quality readings taken using this US approved methodology, with scaling then applied if necessary. The MPCA team intends to install the pods in each zip code during the next month or two. The pods will be powered using a bespoke solar power pack: 30W panels have been specified for such a northern location, compared to the 15W normally required to supply the low-power AQMesh platform. The pods can be battery powered but 12V DC supply was specified, given the 2-year project timescale.
The pods were installed in November 2017 and have achieved 100% uptime to date, including during severe weather conditions, with temperatures below -25°C / -15°F and heavy snow. Initial comparisons against co-located pods show a high level of pod-to-pod precision, with an average R2 of 0.94 for NO2, 0.92 for O3 and 0.93 for PM2.5.
The 50 pods have been compared to the FEM station in two batches of 25, and the first batch of comparisons show an average co-location comparison correlation R2 of 0.74 for O3 and NO2, 0.86 for PM2.5, 0.93 for PM10 and 0.82 for NO. The reference CO showed a baseline shift part way through the comparison period, so that comparison is being reviewed. The SO2 R2 was depressed by a max FEM reading of 2.5ppb, with low FEM resolution, but AQMesh readings were within +/- 2ppb of reference.
The MPCA team is setting up an API connection to the AQMesh server, allowing air quality data to be streamed, near real-time, to the MPCA server, from which it can be published.
AQMesh is in use at various locations in the USA, as well as 35 other countries. The pods deployed in Minnesota are the current production version (v4.2.3).
More information about the MPCA project is available at https://www.pca.state.mn.us/air/assessing-urban-air-quality-project.
* The project is funded by a legislative grant: Environment and Natural Resources Trust Fund (ENRTF) M.L. 2017, Chp.96, Sec. 2. Subd.07b
The team at AQMesh continue to receive many enquiries from smart city initiatives and are concerned that integrators risk undermining entire projects by distributing meaningless or misleading air quality information.
“Many of the people I speak to are used to dealing with sensors that are easy to ‘plug and play’ and expect to be able to do the same with air quality sensors. This is not helped by the fact that most air quality sensors, sensor systems or ‘nodes’, on the face of it, offer very similar specifications”, comments Amanda Billingsley, AQMesh Director. “Quite understandably, IoT professionals do not generally have a background in air quality measurement and are not aware how notoriously difficult it is to get good air quality readings from small sensors, particularly nitrogen dioxide which is known to be so harmful and a key component of diesel fumes – now classified by WHO as a carcinogen.”
Most of the air quality sensors that are small, cheap and low enough energy for IoT applications also have limitations, such as the influence of rapidly changing temperature and cross-gas effects, and a significant level of experience is required to apply the corrections needed to get useable real-time air quality data. At this stage there are two options: one is to try to deal with the challenge in the measurement hardware, such as managing the conditions in which the sensors operate, but this often leads to large and expensive hardware. The other option is smart cloud-based correction algorithms.
Because of the length of time it has been in the field and the huge variation in environments in which AQMesh has been used and validated / corrected, AQMesh is acknowledged through independent studies to be further down this route than any other small sensor system. Even smart city projects which aim to deliver ‘high level’ air quality information, such as ‘the air quality is better here than there’ or some traffic light system, need to be confident that such conclusions are correct if they are not to be challenged by local authorities and stakeholders.
AQMesh is being used in various smart city and IoT projects around the world. In a collaborative smart city project in Cambridge, UK, AQMesh data was analysed by Professor Rod Jones from the University of Cambridge. “Because we know that all the pods read the same and because we have a comparison between one pod and a reference instrument we can say that all pods are working equivalently across the city. What we are seeing is correspondences in excess of 0.7, 0.8, against reference – and that is very good for straight out of the box”, commented Professor Jones.” The study shows that AQMesh can help cities manage air quality, for example by distinguishing between locally and regionally generated pollution, as well as publishing air quality information for the public.
AQMesh measures NO, NO2, O3, NOx, CO, SO2, PM1, PM2.5, PM10, temperature, pressure and relative humidity in a small pod which can be mounted in a post, on a wall, outdoor or indoor. Batteries, solar power or 12V DC power options give flexibility of mounting to capture air quality data from any point in a smart city or elsewhere.
At the IAPSC in May 2017, Professor Rod Jones of the University of Cambridge presented his case study on large scale deployment of sensors, which included showing how AQMesh can be used to discriminate between local sources of pollution and regional sources of pollution.
The study also found how modelling captures the magnitude of an event, but not the timing, and concluded that AQMesh captures spatial gradients very well.
Smart city projects pursue the vision of instrumenting a city with a large number of measurement ‘nodes’ and distributing this information to a range of stakeholders. But at that point different priorities emerge: IT teams are attracted by how readily data can be integrated and communicated whilst air quality professionals focus on how meaningful the air quality readings are.
Air quality readings from traditional air quality monitoring instruments – those which offer the most accurate readings – are generally accessed by direct download from the hardware or by hard-wired data infrastructure. A new generation of cloud-based air quality monitoring devices offers cheaper, smaller, more flexibly located measurement nodes, with all the benefits of cloud data management and integration. Leading air quality small sensor system, AQMesh, offers smart city partners an API data stream, which allows straightforward integration of real-time pollution gas and particle measurements into the smart city platform, and many low cost sensor systems offer something similar.
This is all very appealing and appears to bring air quality measurements into line with the array of city-wide measurements that the Internet of Things is expected to offer to a smart city. However, what if the air quality readings communicated to the public and other stakeholders are misleading, suggesting that air is clear when it is not, or suggesting that the city has a pollution problem that it does not? Either of these scenarios undermine the core case for smart city integration of air quality information. Read more…
Air quality professionals quite rightly demand evidence of accuracy from any new source of air quality readings. The most practical measure of accuracy is to compare a small sensor system which is co-located with – so measuring the same air sample as – a validated air quality station using reference method equipment. Laboratory test results are sometimes offered but small sensors may perform well in lab tests which use single, dry gases, but not in real-world monitoring where gases and particles are mixed and subjected to rapidly changing environmental conditions, such as temperature and humidity. The AQMesh study in Cambridge demonstrates the legitimacy of some small sensor air quality data.
AQMesh uses cloud-based correction for these influences to offer the best accuracy currently demonstrated by micro-sensing units. Teams of leading air quality experts are working worldwide with AQMesh and years of challenge and shared experience in a range of climates and conditions has allowed data processing to be refined to give reliable readings. This accuracy is combined with a robust platform and smooth data integration package to give the lowest possible risk and fastest solution for smart cities.
Smart city projects increasingly seek to include air quality measurements. If city authorities and the public are being asked to act based on air quality readings they must be credible. Whilst cheap sensors may offer easily integrated readings, they offer poor value for money if the information they produce cannot be trusted by the public, smart city project managers and stakeholders.
The search is on for low cost air quality sensors which can be easily integrated into the chosen IT platform. Many commercially available sensors for key air pollutants such as NO2 and PM2.5 are working at their limits and, although these may seem “low cost”, often disappoint if adequate correction is not applied. Even sensors that are sensitive enough in a laboratory may struggle to distinguish a signal from the target gas or particulate matter from noise due to platform electronics, environmental conditions or interfering gases. Failure to adequately manage or compensate for these effects can mean that inaccurate readings from monitoring nodes are published.
Unfortunately individual air quality sensors used in isolation are not able to accurately measure air pollutants at the parts per billion levels required by current air quality legislation. A smart sensor system is currently the only way to overcome these issues and obtain data with any real value.
AQMesh is a sensor system which measures NO, NO2, O3, CO, SO2, PM1, PM2.5, PM10, TPC, noise, temperature, humidity and pressure in a single, compact unit with independent power and communication. Years of development have fine-tuned the performance of processing algorithms to give proven precision and accuracy. Multiple examples can be seen at https://www.aqmesh.com/performance/co-location-comparison-trials/, as well as a real-time feed comparing live AQMesh pod readings against those from a co-located reference station. The system has the added benefits that it is very quick and easy to install, is robust, can operate in environmental conditions from -20°C to +40° and has various data integration options.
Indoor air quality can also be controlled by smart buildings. In many cases HVAC systems bring in ‘fresh’ air to address CO2 build-up, but in cities that air is likely to be polluted – from NO2 and possibly from particulates. A smart system can control where air is drawn in and ventilation rates, depending on air quality at the various inlets, allowing optimisation of the internal CO2, temperature and humidity whilst minimising external pollutants brought into the indoor space. AQMesh pods can be readily installed at various heights outside and inside buildings, all feeding near-live data to a central control system. Read more…
Early versions of AQMesh were used across eight cities in a European funded Citi-Sense project ending in 2016, and performance has improved significantly since then, to the results seen in a recent Cambridge smart city pilot study (see https://www.aqmesh.com/cambridge/). AQMesh is now being widely used by national, regional and local government authorities across Europe to supplement their much more expensive reference monitoring locations and is providing valuable information to inform smart city and smart building strategies leading to better air quality for all.
- Research shows that increasing the number of measurement points improves the spatial resolution of urban air quality models.
At the RSC AAMG event on ‘Air Quality Monitoring: Evolving Issues and New Technologies’ Professor Rod Jones of the University of Cambridge presented a paper showing very encouraging results. “Because we know that all the pods read the same and because we have a comparison between one pod and a reference instrument we can say that all pods are working equivalently across the city. What we are seeing is correspondences in excess of 0.7, 0.8, against reference and that is very good for straight out of the box”, commented Professor Jones.
These findings are from a project in Cambridge where 20 pods, initially co-located at the AQMesh UK factory, were placed at key points around Cambridge. The objective was to demonstrate what could be shown about ambient air quality at key points in the city, using a larger number of measurement nodes to understand how air quality varies across the city, particularly in relation to key transport corridors and areas of construction activity.
The 20 AQMesh pods measure gases (NO, NO2, O3, CO and SO2, particulate matter (PM1, PM2.5 and PM10) and environmental conditions (atmospheric pressure, relative humidity and pod temperature). 19 of the pods are powered by lithium battery and have been gathering data at 15 minute reading averages since June 2016, without any need to visit the sites to change batteries or carry out maintenance. The twentieth pod is currently running at one minute reading intervals, mounted at a Cambridge City Centre reference station, using a high capacity lithium battery. Each pod is small enough to be easily mounted to a post, wall or enclosure and all pods have been functioning without fault throughout the project.
As part of the project, data has also been pushed directly from the AQMesh server to a University of Cambridge server where it is automatically displayed in near real time. A further aspect of this initial project is to compare collected AQMesh data with ADMS-Urban modelled data for the same area and then use the real-time AQMesh data to improve the airTEXT air quality forecasts for Cambridge.
The next steps are to calibrate the pods and to analyse the data in more detail. Co-locating one of the pods with the reference station has allowed slope and offset values to be calculated, as all pods had already been co-located, allowing the same scaling to be applied to all pods. These values can then be applied to the AQMesh server, improving the accuracy of all data gathered after that point. Initial analysis using wind rose plots has shown the extent to which pollution can be attributed to local road traffic at each point. Further analysis of data will show how pollution varies across the locations and by time of day or week.
It is generally accepted that whilst measurements from air quality reference stations are highly accurate, they are not sufficiently location-specific. Key pollutants – such as NO2 and PM2.5 – vary dramatically over short distances and time intervals, but the large size, maintenance requirements and relatively high cost of reference equipment limits the places it can be installed. Diffusion tubes can offer a very cheap alternative and are much easier to install in specific locations, however they only offer a single reading over a number of weeks, and air quality professionals therefore rely on modelling techniques to fill the gaps. With research continuing to prove the extent to which air pollution varies significantly over space and time, the answer would be a reliable and accurate tool for taking real-time, localised measurements.
A number of new low-cost air quality monitoring systems are available, each with benefits and shortcomings. It is fair to say that the available sensors, whether electrochemical, optical or metal oxide, are all working at or close to their limit of detection to provide the low ppb or µg/m3 level of sensitivity required for any of the common ambient air quality applications. However, several systems offered for these applications provide readings in ppm or even % level readings – which clearly makes them inappropriate for ambient air monitoring. Some are also not fit for long-term outdoor use, as they are not fully weather proof or cannot cope with the expected temperature ranges. However, at least one system – AQMesh – does operate across a wide range of conditions and territories, so having established that a viable product exists, can it deliver the accuracy required?
Performance is clearly a major consideration for any user and comparing readings from a lower cost system against a reference station is the obvious place to start. One immediate challenge is ensuring meaningful results. Particularly in roadside applications or where there is an immediate source of pollution, all sensors and intakes must be within a metre of each other and at an equal distance from the immediate source. Most sensors, not unreasonably, also require an uninterrupted air flow around them – mounting immediately above hot or wet surfaces will not give accurate readings. On the other hand, some limitations of reference equipment come to the fore when comparing with a different type of measurement. For example, single channel NOx analysers switch between measuring NO and NOx, calculating NO2 as the difference. This switching can have dramatic effects on readings for the two gases (which are measured separately and directly by other sensors) at short reading intervals, such as 1 minute. Similarly, any differences in clock synchronisation or reading averaging protocol (time beginning or time ending) can make the difference between a regression comparison R2 of 0.9 and 0.1, which can render comparisons meaningless.
Comparisons of particulate measurements are also problematic due to the range of reference-equivalent methods available and the limitations, in many ways, of the reference method itself. Since the expanded uncertainty of the reference equivalent measurements for PM10 and PM2.5 allows up to 25%, this should be borne in mind when making comparisons with lower cost particulate sensors. Overall, for both gases and particulate matter, if several identical low cost systems are co-located, the user should expect a high level of repeatability (R2 > 0.9) and should expect to be able to adjust accuracy by ‘calibrating’ – adjusting slope and offset – against a co-located reference/equivalent station. Some systems, such as AQMesh, then allow this scaling adjustment to be applied automatically to all future readings, minimising the need for manual data correction. Access to a calibrated reference station and careful co-location is currently key to getting value out of any of the current generation of emerging sensor systems, although the objective of good accuracy without the need for a reference station is being actively pursued.
First questions about these systems often include ‘How do I run gas through it to calibrate it?’ and ‘Can I calibrate (or test) it in the laboratory?’ In systems such as AQMesh the air sample is not pumped, for good power-saving reasons (low power is essential for battery operation), and so it is not obvious how a conventional gas calibration would work. More importantly, although the sensors generally do give very good results in laboratory tests with known dry, single gases, these bear no relation to real ambient field measurements with a combination of damp, humid gases at potentially varying temperature and pressure. Overall, there is no proven substitute for co-location with a reference station. Even with all of these considerations, some of these small, lower cost air quality systems, such as AQMesh, can deliver very impressive comparison results and provide a new source of air quality data. Those with in-built power and communications offer genuine freedom to gather measurements from any location and research teams worldwide are using such systems to understand pollution around cities, inside and outside buildings, at different heights, in street canyons, around industrial facilities and within neighbourhoods, at different times of day, and so on. This new granularity of measurement and flexibility of location gives air quality management teams a real tool to carry out ‘before and after’ studies and evaluate a range of policy or pollution mitigation activities. Where a number of sensor systems are used, and particularly in combination with wind speed and direction information, the relative measurements and source distribution can provide very powerful insights about where to target pollution mitigation activity.
One such low cost outdoor air quality monitoring system offering this type of flexibility is AQMesh, which has proven its repeatability, accuracy and performance through a series of these careful co-location comparisons with calibrated reference stations in a variety of global locations and applications. The small size, battery power and wireless communications technology mean users can benefit from reliable and accurate real-time, localised air quality measurements in a broad range of studies.
How accurate is ‘accurate’?
One area of discussion is what level of accuracy is ‘good enough’. Although this depends on the application, it is still tempting to look for a very high level of agreement between the low cost sensor system and reference equipment. Whilst this may be the goal, the lower cost systems are considerably cheaper and have the benefit of being correctly located so perhaps it is better to have slightly less accurate readings from the right location than highly accurate readings from the wrong location? For some applications it is really only the relative readings which are required, and systems like AQMesh provide very high levels of precision between identical systems. Or it may only be appropriate to provide a ‘traffic light’ indication for communicating air quality to the public. Until more general guidance is available, users will have to take a view on accuracy relevant to their application.
Publishing air quality data
Another area of confusion is regarding data privacy vs online publication of air quality data. Most of the new air quality systems take advantage of remote data management and online access. This makes sense for a number of reasons. Hard-wired communications infrastructure is a barrier to freedom of location and new systems generally communicate either using the mobile network, radio or wi-fi. Online access to data is also very convenient and less resource hungry. Few of us who readily use mobile phones, online banking and many of the commonplace applications of modern life fully understand security of communications and the reality of data hosting. The bottom line is that air quality data from sensor systems using wireless communications can be as secure as any other online application. Confusion is caused by the systems which are focused on citizen engagement and offer automated sharing and publication of data, but these are the exception and in most cases, such as AQMesh, data is private and secure.
The new generation
Current low cost air quality sensor systems are a very mixed bag. Some products may well appear to offer the same measurements and even claimed accuracy as the more thoroughly developed and tested systems and the user has little choice but to ask searching questions and ask for demonstration of performance and reference projects before purchasing. But the need for such systems is clear and performance is already good enough for many leading institutions and organisations to be actively using the technology. Sensor and sensor system manufacturers are seizing on every new shared comparison dataset and development in technology to make further improvements. The insights that these sensor systems can offer are real and relevant and there is no substitute for trying the technology in any given application to see what it can offer. Many users have found that one insight can lead to another and, working with a clear understanding of the strengths and weaknesses of the systems, the benefits of making a start with this new tool are overwhelming.
The emergence of sensors capable of measuring the gases and particles that make up air pollution, especially in cities and industrial areas, has driven many academic studies which evaluate the sensors and compare performance against reference methodology. Such projects provide valuable and thorough assessment, but they currently work slower than the pace of low cost sensor system development. In addition, EU and US authorities are developing methodology appropriate for certification of such systems. In the meantime, practitioners across a number of fields are adopting AQMesh as the leading commercially available sensor system, and generating valuable information to support policy and commercial decisions.
The obvious and first application for this sort of technology is in identification and management of pollution ‘hotspots’ in cities and collecting background measurements across a much wider range of locations than has previously been possible. UK local authorities and similar bodies in a range of countries have been using AQMesh to monitor specific locations for NO2 and now particulate matter, evaluating mitigation methods, such as barriers between traffic and pedestrians. These studies have often been in conjunction with academic teams who have also investigated issues such as the impact of industrial chimneys close to high rise buildings and pollution at different levels of multi-storey residential buildings. One project uses AQMesh to support development of a walking-to-school campaign, comparing different walking routes and educating parents. AQMesh has also been used to minimise NOx and particulate matter inside buildings through management of building ventilation systems.
Building contractors have been searching for an instrument to measure dust construction sites, which does not require an external power source, and a number of projects are now using AQMesh for this purpose. Civil engineering applications include monitoring pollution in road tunnels and associated ventilation ducts. Studies in several countries, including Scotland, Ireland and Greece focus on understanding the relationship between traffic volumes, mitigation measures and air quality. Local air quality data, used in combination with wind speed and direction information, can provide powerful pollution source attribution, relevant to fence line monitoring of industrial sites, airports, and so on.
These new sensors systems can provide a new stream of information, complementary to and calibrated by reference stations. But being self-sufficient in terms of power and communications, they offer freedom of location and open new opportunities.
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