Explore AQMesh

Looking behind the scenes of dust & PM monitoring

20-May-2024Industrial | Particle monitoring | PM | Product

Looking behind the scenes of dust & PM monitoring

Measuring particulate matter (PM) accurately comes with a number of challenges, including effects from humidity and differing particle sizes. Technological considerations are also a factor, such as variable sample flow rates and the physical size and diameter of the sample path, which could affect the number of particles able to be measured.

AQMesh has been able to overcome many of these challenges through its proprietary OPC development, making it a robust, reliable and accurate solution for PM monitoring. From sample inlet to final data output, each design requirement for precise measurement of particles in ambient air has been carefully thought out to result in a truly bespoke and fit-for-purpose optical particle counter (OPC) – a solution that only AQMesh can offer. There are a few key aspects:-

Active sampling using a pump

By using a pump instead of a fan, the AQMesh OPC samples at a steady flow rate from the inlet to sensor, which provides a more consistent air sample than other methods used. Systems which use fans run the risk of creating vacuums, which can interrupt the flow rate and affect the sample measurement.

Laser-focused

A funnelled inlet helps the OPC taper the particle samples to a focal point, and then a straight line sample path from this focal point to the laser bench means larger particles are not ‘stuck’ in a bend and ensures all particles within the sample pass through the laser path, allowing for complete capture of particles, categorised by diameter from 0.3 – 30um. This means the laser OPC in AQMesh gives a true PM10 measurement, which many systems – including nephelometers – cannot offer.

Heating the sample to reduce deliquescence

The optional heated inlet allows AQMesh to reduce the effects of humidity on particle sizes. Known as deliquescence, this effect can make particles larger in diameter due to the absorption of moisture. The heated inlet overcomes this by drying the sample as it is drawn in, bringing the particles back down to their true size and therefore resulting in more accurate measurement. Additionally, AQMesh can detect when deliquescence is likely to have happened during data processing and can ‘flag’ the data point – including with non-heated samples – allowing it to be easily identified and redacted. Use of the heated inlet results in less than 1% of data points being flagged in this way.

Autonomous power for uninterrupted sampling

Using AQMesh’s bespoke smart solar pack for autonomous power allows for uninterrupted PM monitoring, with no need to change the sampling regime to take fewer readings – a process which could potentially void an instrument’s MCERTS certification. The AQMesh solar pack provides consistent, smooth power all year round for AQMesh pods.

Minimal maintenance

Other benefits of the AQMesh OPC include reduced maintenance – there is no need to change any filters, and there is no need to replace the whole OPC unit when it requires servicing. We simply advise the pump and laser is replaced every two years, which can be carried out by the user without returning the instrument to factory. Exceedance alerts can also be set for PM fractions, alongside any other pollutants being measured, which enable users to receive immediate information if levels breach a user-defined level over a user-defined period.

MCERTS indicative

AQMesh has been accurately measuring PM for over 10 years, and offers the added reassurance of MCERTS Indicative measurements for PM2.5 and PM10.

For more information on how AQMesh can support your PM monitoring requirements, contact our experienced team today.

Supporting your air quality monitoring system when you can’t get to it

24-Apr-2024Fenceline | Hybrid networks | Industrial | Networks | Product | Support

Supporting your air quality monitoring system when you can’t get to it

Each time we think we have found a spectacularly remote monitoring location, an even more inaccessible spot is reported by one of our users. Full-day trips to visit a location have now been beaten by customers who need to charter a plane to reach them. So, remote diagnostics and support are very important.

Luckily, IoT communications, cloud data management and over 10 years of experience supporting AQMesh have allowed us to continually improve our ability to supply and support AQMesh in remote locations. Pods have been used from the edges of the arctic to undeveloped deserts – as well as on ships – with the help of a few features.

Robust design, low maintenance intervals

AQMesh was designed to be rugged, for use all over the world and with an expected maintenance interval of two years. We have always understood that field maintenance requirements must be kept to a minimum, and pods operating for year after year, in the harshest environments – from deserts to extreme cold – demonstrate design effectiveness. This includes protecting electronics from the elements and mitigating electromagnetic interferences, as well as taking measures to keep insects, wildlife and birds out/off.  The unobtrusive pod design has also ensured a very low rate of vandalism and theft.

QA flags and notifications

The AQMesh data stream includes vital pieces of information which allow users and the AQMesh support team to check that pods are functioning correctly and provide an early warning system. Users can register for email notifications for their pods – it is always better to find out that power is running low or data is no longer being transmitted at the time, rather than when the project ends and it’s time to review data.

Remote scaling / calibration

Whilst AQMesh was a leader in co-location comparison and the ‘gold pod’ technique for in-field calibration, these approaches do require regular site visits to move pods around. We have now developed a method that can provide remote calibration of a sensor network, with or without an available reference station, that does not rely on artificial intelligence.

Diagnostic information

The AQMesh team can access additional diagnostic information remotely, such as performance indicators from the optical particle counter, solar pack battery voltage or sensor failures. Some of these indicators are available to users via their secure online or API access, and some can be used by our global technical support team. The team uses the full range of diagnostic information available, including SIM connection attempts, to provide free support for the life of the equipment. Their over-riding goal is to fix any problem without asking users to visit the site.

Over the wire intervention and updates

AQMesh firmware developments now allow power cycles to be triggered remotely, firmware to be updated over the wire or remote sampling and transmissions interval changed.

Power

We have learned from the many challenges that power supplies can present to remote operation. Whilst the original lithium thionyl chloride battery offered unbeaten long-term autonomous operation of gas sensors, increasing shipping limitations have turned our focus to direct power supply and solar. We invested in a full technical investigation to identify a mains to 12V DC transformer that could cope with ‘dirty’ power supplies, as well as in-pod measures to manage spiky or intermittent power.

Having seen so many problems from simple solar-panel-plus-battery arrangements, we designed our own smart solar pack, which squeezes the most power out of any location, manages power delivery and provides online voltage measurements. We are mindful that sampling and reading rates are defined by the project – and potentially certification – and the power supply must deliver the same sampling throughout the year. Readings should not be compromised by the difficulty of providing autonomous power.

Communications

The global SIM supplied with a standard AQMesh pod will roam across networks to find the best connection at each transmission, and has proven to be a very reliable way of transferring sensor output from hardware to our cloud server for over 10 years in more than 70 countries. Occasionally, we find that only a single, specific network is available – or a customer would prefer to use their own SIM – in which case we can programme the pod to work with a locally-sourced SIM contract. To achieve autonomous communication, the AQMesh LTE CAT M1 modem uses the latest LTE communications standard, including support for NB-IoT where available. In the most extreme cases, satellite communication is the only viable option and AQMesh can connect via an ethernet port to a suitable modem to connect this way. Reliable communications are key to remote data access and support.

The growing need for remote, long-term monitoring, in all conditions, drives our continuous development from data QA to comms, and we welcome challenges.

“Maintenance-free air quality monitoring” – is it a myth?

12-Apr-2024Maintenance | Networks | Performance | Product

“Maintenance-free air quality monitoring” – is it a myth?

There’s no doubt that small sensor systems can have an advantage over their cumbersome reference station cousins – in terms of maintenance requirements. We are often asked about ‘service’ requirements for our pods and the honest answer is that the default position, in normal working conditions, is ‘none’. However ..

There are consumables, conditions can have an impact and sometimes ‘stuff happens’. We have seen small sensor systems claiming they require no maintenance at all, so would like to offer some thoughts on these three areas:

Consumables

Some sensors and sensor components need to be replaced at a defined interval (two years for AQMesh). This may be because the product is designed to optimise accuracy and component duty cycle, such as the AQMesh pump sampling particulate matter, which is expected to last two years on standard settings. If the pump is not replaced at two years, in-field failure is the likely outcome at some point. AQMesh uses a pump to provide reliable sampling over a set period. An alternative, such as a fan, may not be offered with a finite duty cycle, or with one that is theoretically longer, but failure modes can be undetectable remotely and readings affected. Is that better?

Many small sensor systems use Alphasense’s electrochemical sensors, which come with a recommended two-year life. Sure, they last longer than two years and keep producing numbers, but who has tested the sensors beyond two years and will be answerable for accuracy after two years? Users of these systems need to look ‘under the hood’ here – is the system claiming to be maintenance-free ignoring sensor manufacture advice? Are they reducing operation or sampling to extend the duty cycle?

Monitoring conditions

In a nice, clean monitoring location it is possible to predict performance of a monitoring system over several years. But, when the system is faced with tough conditions – such as sandstorms or an acidic environment – some intervention may be necessary to keep the system running. Good design and remote diagnostics can help to minimise this, but it is often the pods installed in the most remote locations (hardest to reach if necessary) that are hit by the toughest conditions.

‘Stuff happens’

Most of the stuff that happens to AQMesh pods is hard to predict. One academic study, monitoring air quality around treated road surfaces, mounted pods a few centimetres above the road and they were swamped in a rainstorm. One contractor installed a pod on its side. Solar-powered pods are sometimes installed with great difficulty, only to find the system is constantly in shade. We encourage as much pre-installation planning as possible – and provide a wealth of manuals, guides and videos to avoid these scenarios – but there are sometimes situations which require on-site intervention. We have seen ‘maintenance free’ fulfilled by offering replacement equipment under warranty, instead of maintenance, but customers still have to make a site visit anyway, so we don’t really buy that one.

AQMesh started out offering uninterrupted 2-year gas monitoring with autonomous power but we quickly found that much monitoring was project-based and that users preferred to have the comfort of planned maintenance arrangements that would maximise the chances of achieving high data capture and high data quality throughout the project.

Anodes and anemometers for harsh winter air quality monitoring

11-Mar-2024Accuracy | Fenceline | Industrial | Networks | ProductIceland

Anodes and anemometers for harsh winter air quality monitoring

We are often asked by customers whether AQMesh can operate in cold conditions. Long-term use at temperatures well below freezing, with ice and snowfall, is indeed challenging. Cold weather operation has been key to AQMesh – improved upon and proven in the field – for over 10 years. The main features, described below, have been most recently been put to the test in Iceland.

Ölfus, a municipality in Iceland, installed a number of AQMesh pods during December to measure local air quality across the town in relation to the region’s volcanic activity. The pods – supported by Vista, AQMesh distributor for Iceland – will monitor NO, NO2, CO, H2S, SO2 and particulate matter and report the data to the local Environment Agency.

A monitoring network has also been recently installed on a construction site in Reykjavík, measuring dust (PM), NO, NO2, NOx and wind speed and direction, powered by the smart solar pack. AQMesh was chosen because of successful performance in previous deployments in Iceland, as well as ease of installation and minimal maintenance requirements.

The successful operation of AQMesh pods in extremely cold temperatures can be attributed two main factors: power management and weatherproof design.

Power management

Many small sensor air quality monitoring systems use lithium batteries, which carry a recommendation for use only down to 15°C. Lithium ion batteries should not be charged below 0°C – there are risks in trying to do so – and performance is also significantly poorer at low temperatures. This is because lithium ions can plate the anode surface in freezing conditions, reducing battery capacity and increasing resistance.

The AQMesh solar pack uses the heavier but more practical 22Ah lead acid battery, which performs reliably in such temperatures. The AQMesh battery has 264Wh capacity, compared to lithium-based systems which store less than 100Wh solar power. With the battery built into the smart solar pack, capable of powering the pod for 1.5 to 2 weeks without sunlight, the pod can be powered at full capacity over the whole year at surprisingly high and low latitudes. This is particularly significant for relatively power-hungry sampling of PM: AQMesh will continue to sample at the optimal rate and not reduce sampling, which would deviate from MCERTS test conditions, voiding certification. Lead acid batteries are also easier to ship than lithium: a major consideration if you are moving pods around the UK or internationally.

Weatherproof design

Simple design considerations can be vital. Right from the first deployments across North America and Scandinavia, AQMesh design has shown that equipment cannot just survive but provide full functionality through a harsh winter, without maintenance visits. The shape of the pods prevents water, ice and snow building up on the surface, and there are no moving parts that can be affected by freezing temperatures. The AQMesh wind speed and direction sensor option is an ultrasonic anemometer, with no moving parts to wear or recalibrate, making it reliable and low maintenance.

AQMesh pods use a pump for drawing in particles, as opposed to a fan. Fans are more likely to be affected by snow and ice, potentially recirculating the same air if even partially blocked, whereas a pump will still actively draw an air sample.

Data processing on the secure AQMeshData.net server uses correction algorithms based on over 10 years of real-world testing which can compensate for extreme environmental conditions and flag affected data points if necessary.

A network of 50 AQMesh pods in Minnesota, USA, continues to operate smoothly in temperatures as low as -25°C, despite the area being under several feet of snow for long periods of the year. Other deployments include Alaska, Mongolia and Scandinavian regions, all of which experience harsh winter conditions.

For more information and to discuss your potential air quality network deployment contact our experienced team today.

Solar power supplies are not all equal for full-year, consistent AQ monitoring

16-Jan-2024Networks | Performance | Power supplies | Product | Solar

Solar power supplies are not all equal for full-year, consistent AQ monitoring

Autonomous power can make all the difference in hyper-local air quality monitoring. With particulate matter sampling needing a little more power than passive gas sensors, solar is the go-to power option, rather than internal battery. Most systems require sufficiently little energy that they can be powered by a relatively small solar panel, but it’s the back-up power management that makes all the difference.

For much of the higher latitudes of Europe and North America, the challenge is to achieve full-year monitoring – just. What we want is to be sure that no readings are missed in December, but that we manage that without a huge solar panel or battery. Most small sensor air quality monitoring systems are mounted up lamp posts, so weight and size (wind resistance) are real considerations. As always, the devil is in the detail. Users should beware of ‘winter sampling’ settings, which reduce PM sampling during low solar power months, meaning each 15 minute reading may be based on as little as one minute of sampling. This is particularly relevant when the sampling regime is linked to certification, such as MCERTS.

The AQMesh smart solar pack power supply option provides consistent, smooth and autonomous power all year round for an AQMesh pod. The pack is much more than just a solar panel, with the true benefit lying in back-up power management: it’s about powering the pod when the sun is not shining.

The solar pack is quick and easy to install – even up a ladder – and comes with flexible mounting options for posts and walls. Guidance is offered for safe, straightforward installation of the pod and ‘all in one’ solar pack, working at height. The solar pack is a compact unit with an adjustable angle for maximum solar harvest. Setting the direction and angle of the panel correctly at installation makes a significant difference to solar yield, even if no further adjustments are made for years. The simple single connection to the pod is the same as that used with the AQMesh standard weatherproof DC power supply, so solar can be easily interchanged with direct mains power, if ever required. The solar pack also features an additional connection to power a second pod at the same time, which helps when co-locating pods for short periods.

Smart functionality allows the charger to efficiently maximise solar harvest, maintaining battery health and extending the life of the battery. Using ultrafast maximum power point tracking (MPPT), the system monitors the voltage and current outputs of the panel to ensure optimum solar harvest during changing weather conditions and light intensity throughout the day. It also features an intelligent load output function with over-charge protection – preventing excessive drain on the batteries – and ensuring that a full 100% recharge will be attempted every day. Charging and battery voltages are among the key pieces of information that can be checked on site using a smart mobile Bluetooth app. Used by AQMesh and customer technicians around the world, quick access to information allows speedy diagnosis of any issues on site, and battery voltage information is also available alongside readings on the secure AQMeshData.net server.

Another consideration is the type of back-up battery used. Many systems use lithium ion batteries, which should not be charged – or re-charged, as a back-up battery – at temperatures below 0°C, with a recommended operating range of 15°C to 35°C, making them unreliable for winter solar back-up. Lithium ion batteries can also be problematic for shipping, with even a small quantity of lithium classed as ‘dangerous goods’, bringing transportation limitations and delays. The AQMesh solar pack uses an AGM lead acid battery, which has sufficient capacity, will continue to operate throughout cold temperatures and is easy to ship and replace.

This efficient solar charger means that even during periods of poor weather, the smart solar pack can power an AQMesh pod consistently – all year round – across the UK and Europe, based on standard measurement settings, with no need to reduce the sampling regime.

From Alberta to Scotland – and many points at lower latitude – AQMesh users around the globe are benefiting from uninterrupted power supply thanks to our bespoke and proven solution for autonomous, wireless power.

How do you calibrate a small sensor air quality system?

24-Oct-2023Performance | Product

How do you calibrate a small sensor air quality system?

First of all, you can’t calibrate using bottled gas, as with reference analysers. Even if you can create a chamber or manifold to pump gases through, electrochemical gas sensors do not respond in the same way to single, dry gases as they do to mixed gases in an ambient environment. And that sort of ‘laboratory’ approach is even more difficult with particulate matter – we have seen huge resources devoted to mixing particles in a chamber, but it is very hard to achieve a known, consistent level against which to calibrate.

Small sensor systems are best calibrated by co-locating one or more units as close as possible to the intake of a reference or equivalence standard analyser, whether for gas or PM. Access to a reference analyser varies depending on the number available locally and also local authority policy regarding access. Mounting lots of small sensor systems in the confined space of a reference station is not easy, particularly finding clear space for power supplies, including solar. In this case, the ‘gold pod’ approach is effective: calibrate one unit against reference and then co-locate that unit against each of the others in turn, or with them all mounted together in a more convenient location. A couple of things to remember:

  1. Some pollutants are poorly mixed, eg: NO close to source, so levels can vary dramatically over short distances: we consider a true co-location to be no more than a meter between sensor and reference inlet

  2. Pollutant levels at the co-location site need to be appropriate – avoid sites where levels are very low, as calibration is likely to be unsuccessful and would result in low accuracy at locations where levels are higher

If a reference station is not available, diffusion tubes or passive samplers can be used instead. Both approaches offer traceability to a certified standard, and therefore provide a route for data quality assurance. We can provide a tested methodology for calibration against diffusion tubes.

As co-location as a means of calibration involves equipment movements (potentially many unit installations and de-installations), this approach can be resource-hungry. New methodology is now being used which can calibrate a network of small sensor systems against a reference station in the area, and is a service AQMesh offers.

A final word: beware ‘self-calibrating’ systems. If it uses machine learning for its data processing, then it will be optimised for the location and conditions of where it was calibrated, and the unit cannot be reliably deployed anywhere else with confidence in the calibration. In addition, the processing used to calibrate is not an ‘empirical correction’, so it is not repeatable or traceable to reference or similar instruments within its network.

Why is renting small sensor air quality monitoring systems not more popular?

18-Oct-2023Product | Rental

Why is renting small sensor air quality monitoring systems not more popular?

We know from our customers that they are often monitoring for a particular air quality project, although some are monitoring on an ongoing basis. So why do they always want to buy equipment rather than rent it? With renting you always get the latest equipment version, new sensors, all costs included, full support and even a discount off purchased equipment.

Sure, it’s cheaper to buy when you get beyond two to three years, but sometimes we get the impression that this sort of equipment is not expected to last longer than that (with a 5-year pod warranty and plenty of pods over 10 years old still in use, we don’t know where that view comes from). Is it about capital vs revenue budgets? Is it driven by the tender process?

Anyway, we don’t mind. We’re ready to ship rental or purchased pods with a two-week lead-time, so rent or buy, as suits you.

Technology + tenacity = lifetime AQMesh global support

17-Apr-2023Performance | Product | Support

Technology + tenacity = lifetime AQMesh global support

AQMesh small sensor air quality monitoring systems have been in use around the world for over a decade now, but it remains the case that support challenges are always greater with:-

  • New customers, unfamiliar with the product
  • Located a long way away (distance, time zones, business culture)
  • In difficult conditions (environmental, infrastructure)
  • With little or no knowledge of air quality monitoring
  • Working at the end of a long chain of parties

Whilst any one of these points in itself makes user support harder, the AQMesh team have energetically pursued the ideal of providing great support, even when all five challenges apply.

To illustrate this point, we can tell the story of 16 pods used in Bangladesh, Pakistan, Vietnam, Philippines and Mongolia. AQMesh was chosen for this project, funded by an international bank, coordinated by an international consultancy and procured through a UK distributor. The pods were shipped in April 2020 all measuring PM and a combination of gases including NO2, O3, CO and SO2 using mains and solar power. Most pods were installed easily, as AQMesh is designed for quick installation, by simply connecting the power supply and using the standard fittings provided to mount to a post.

In November 2020 two pods in Philippines were reported as ‘dead on arrival’. As the cause for this failure could not be quickly established remotely or through the chain of communication, two new replacement pods were shipped and it was confirmed they were functioning normally as soon as they were installed. Inspection of the two returned ‘dead’ pods indicated that the pods had been internally re-configured since they left the factory: this sort of curiosity is not unknown, and it is rare that any party wishes to hold their hand up, so the issue was not pursued further and all of those involved in the project were happy to see all pods delivering data. In February 2021 it was agreed that AQMesh would take over direct support of the pods, as it streamlined support by no longer communicating via the UK distributor.

By April 2021 some sensors had been replaced under the no-quibble 12 month warranty and the AQMesh team was explaining why data is redacted in ‘extreme conditions’. Briefly, all electrochemical sensors produce less stable output when subjected to high temperature and low humidity, often showing artificially elevated readings. AQMesh identifies and flags data under such conditions and the default is to redact flagged data, which avoids likely over-reads being reported. Even in the most extreme global environments, redaction leaves data delivery well above the 90% target set for conventional air quality monitoring equipment.

In September 2022 the international consultancy confirmed that their project had finished. The only way the pods could continue being used in the countries was through direct support from AQMesh, so the chain of communication shortened further and AQMesh offered to continue to support the pods, using the free weekly data delivery service.

To date the AQMesh team still supports the pods, free of charge, and recently resolved communication problems with pods in Pakistan which had been caused by environmental debris blocking the solar panels used as the power supply. One pod is now being returned to factory to be investigated, repaired and returned to the user.

AQMesh has always prided itself on its customer service. There is no cost for technical support and location continues to prove it is not a barrier. A wealth of online training material is provided in addition to remote technical support and smart remote diagnostics, including power cycling, re-stabilisation and sensor rebasing. Users also benefit from free remote firmware upgrades for the life of the product and free of charge data processing algorithm upgrades for gas channels, which means customers can be reassured they are always the using the most up to date technology available, giving them the most accurate and reliable data possible.

AQMesh manufacturer achieves ISO9001:2015 certification

15-Sep-2022Company news | Product

AQMesh manufacturer achieves ISO9001:2015 certification

Environmental Instruments Ltd, the company which manufactures AQMesh, is delighted to announce it is now ISO9001:2015 certified. ISO9001:2015 is the standard which confirms a business is using its quality management system and processes effectively and consistently to meet the requirements of its customers.

The achievement of this standard endorses the AQMesh team’s claims that it works to the highest standards of quality when designing, developing, manufacturing and supplying AQMesh pods, as well as offering excellent customer service and support at all stages of the customer experience.

Continual improvement of the customer experience and the products AQMesh offers has always been integral to its aims to provide innovative and market-leading solutions for localised air quality monitoring.

Having ISO9001:2015 certification means both new and existing users can now have even more reassurance they are receiving the most proven small sensor air quality monitoring system, from the most experienced team in the industry. Gaining ISO9001:2015 certification also enables further certification opportunities for example, MCERTS indicative and CEN/TS 17660-1:2021.

Amanda Billingsley, Managing Director at AQMesh, says “The whole AQMesh team has embraced the ISO9001 mindset and we have used this process to identify opportunities for improvement, as well as flying through the audit on the basis of our existing robust processes. This certification is just a milestone in our journey towards ever better customer focus, quality management and innovation.”

10 things AQMesh did first

31-Aug-2022Accuracy | Performance | Product

10 things AQMesh did first

2022 marked 10 years of innovation and leadership from AQMesh. To highlight the team’s experience, ongoing forward-thinking and its commitment to pushing the capabilities of small sensor systems, here are the top 10 things AQMesh developed first and refined since it commercially launched in 2012.

1. IoT connectivity using the mobile phone network: remote data for small sensor air quality monitoring

AQMesh was the first small sensor manufacturer to adopt an IoT approach, using the mobile phone network to connect with the cloud, allowing remote access of data from individual measurement points. Until then, conventional equipment used loggers and other early small sensor air quality equipment offered direct download or radio communication, often across a group of sensor nodes.

2. Integration of gas and PM monitoring in a single small sensor instrument

Since 2013, AQMesh pods have been able to monitor gases and particles in one instrument. The compact pods have continued to lead in terms of the wide range of measurements offered on a single unit: up to six gases out of NO, NO2, O3, CO, SO2, H2S, TVOC and CO2 as well as PM monitoring and options for noise and wind speed/direction. Pressure, relative humidity and pod temperature are all measured as standard. In the 2019 AIRLAB International Microsensors Challenge, AQMesh was recognised as the most accurate multi-parameter outdoor air quality monitor, and was evaluated for the highest number of pollutant measurements offered within a single system.

3. Mini optical particle counter, counting and sorting particles by size, for accuracy across all PM fractions

AQMesh’s in-house designed optical particle counter measures particulates PM1, PM2.5, PM10, TPC and TSP (up to 30 microns). Its bespoke design uses a straight line between the sample inlet and bench, meaning larger particles do not settle in a bent sample path, allowing for complete capture of pollutants. Additionally, the OPC uses a pump instead of a fan, which produces a steady flow from inlet to sample measurement, and subsequently provides consistency for the sample calculations – fans can cause vacuums which could interfere with the flow rate and affect the sample measurement. The AQMesh OPC therefore allows more coarse particles (PM10) in the sample to be accurately measured.

4. Pioneers of city-wide small sensor networks from Citi-Sense to the Breathe London Pilot

Initiated in 2012, AQMesh was part of the EU-funded consortium which set up a ground-breaking project to advise citizens about air quality, across eight cities, using hundreds of measurement devices. The Breathe London pilot, which ran from 2018 to 2020, and in which 100 AQMesh pods were used, was the world’s first hyperlocal monitoring network. The two year pilot project proved & validated small sensors for city-wide monitoring, and also led to the Environmental Defense Fund (EDF) publishing a ‘blueprint’ for other cities.

5. Real-time out-of-the-box accuracy with correction for environmental conditions and cross-gas effects without the need for machine learning

AQMesh’s high accuracy and performance has been achieved through years of extensive global co-location comparison trials against certified reference equipment, in all seasons, meaning AQMesh can accurately operate in the widest possible range of environments and conditions. No other manufacturer has access to the wealth of data that AQMesh has gathered. With these datasets AQMesh has been able to develop meaningful correction of cross-gas effects and interference from environmental conditions through its fully traceable data processing algorithms.

6. ‘Gold pod’ approach

The ‘gold pod’ approach, as originally described by the AQMesh team, involves one unit being co-located with and scaled against a maintained reference station and then moved around a network of nodes to calibrate each of the other units. This method has now been widely adopted and offers an effective way to improve accuracy and achieve traceability. It was back in 2017 when Professor Rod Jones from the University of Cambridge presented the results of the ‘gold pod’ approach in which 20 AQMesh pods were deployed across Cambridge after co-locating one with reference, and he commented at the time “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.”

7. White reflective sunshield and insulation for temperature management

The sunshield was first added to AQMesh pods in 2013 to minimise the impact of direct sunlight on pod sensors. Various solutions were tested – for active or passive cooling – and AQMesh’s reflective shield, insulation and air flow gap was found to be most effective at minimising the challenge to temperature stability from strong, direct sunshine.

8. Promote rigorous QA/QC and offer feasible methods to achieve it

Since 2015, the AQMesh onsite reference station means each sensor has been tested through a rigorous quality control process before it leaves the UK factory. The custom-built enclosure uses climate-controlled reference/equivalence analysers sampling air from an ambient cage which can hold up to 100 AQMesh pods at a time. This ambient characterisation during manufacture is part of a stringent AQMesh quality assurance process, which also includes strict criteria for PM, so every AQMesh pod out in the field to date has been through specific quality control measures to ensure the efficiency and reliability of each sensor in real-world conditions. QA/QC doesn’t end at the factory either; the AQMesh team regularly offer remote QA/QC of data once pods are out in the field.

9. CO2 emissions profiling

AQMesh can offer incredibly high out-of-the-box accuracy (typically less than 15% uncertainty) for CO2 monitoring. Using this reliable data, AQMesh can be used for CO2 source apportionment, and measuring alongside NO and NO2 can allow for emissions profiles for different locations to be determined. This means the combustion contributing to the pollution can be specifically identified; such as whether there is either gas or diesel traffic, which is only possible with such accurate data.

10. Long distance scaling

The Breathe London pilot showed how pods could be traceably scaled across a city, using a novel approach pioneered by partners at the University of Cambridge. This technique, which reduces the field demands of the proven gold pod approach, requires basic measurement data of a good quality in order to be effective, and AQMesh have built on the initial Breathe London methodology with their own simplified Long Distance Scaling tool.