Our hydrogen sulphide (H2S) monitoring journey literally started in the sludge lanes of a UK wastewater treatment plant in 2017. Since then, AQMesh has been used effectively in a range of applications.

Monitoring H2S in air at levels of less than one part per billion – well below the level at which the human nose can detect this odorous and harmful gas – AQMesh can be used both to measure very dilute levels and where concentrations are significant. These small ‘pods’, with autonomous power and communications, can be quickly installed around a boundary, providing 24/7 monitoring. Near real-time readings are accessible on a laptop, phone or via alerts, indicating where H2S levels have exceeded a set threshold. This core capability has been used in various sectors.

Waste water, landfill and waste management

As H2S smells unpleasant – and may be released as a fugitive emission alongside other odorous gases, such as ammonia and mercaptans – AQMesh has been used to monitor air quality at site boundaries. The AQMesh team cooperated with a UK water utility in 2017 to prove the accuracy of the AQMesh sensor against a Honeywell SPM Flex, showing very good correlation.

During the monitoring period the AQMesh pods were moved from an outdoor monitoring location to indoor, and this saw a significant uplift in H2S levels. Across this range (0 to over 100ppb) the correlation with the Honeywell unit was very strong, at an R2 of around 0.9.

Since this original study, AQMesh has been used to monitor at landfill and waste management sites around the world, including New Zealand, Iceland, South Africa and UK. Continuous, real-time boundary measurements can be used to investigate odour nuisance complaints, with alerts set up if concentrations exceed agreed limits, over a user-set time interval. As pods are deployed closer to the source of emissions, monitoring can be used to alert operators to high levels of H2S, as well as other pollutants. Action may need to be taken, such as enclosing spaces or protecting staff from inhaling elevated levels of pollutants.

Industrial processes

Linked to H2S from waste, AQMesh is currently being used to monitor H2S levels at a site close to a biorefinery plant, where measured levels of the gas show regular peaks.

Other industrial processes where real-time H2S monitoring can add value are the oil and gas industry – particularly relating to sour, or sulphur-heavy gas, and oil sand extraction – as well as lime manufacture and paper processing. The most common air pollutants generated by the pulp and paper industry are nitrogen oxides, sulphur compounds, particulate matter (PM) and volatile organic compounds (VOCs), all of which can be monitored by a single AQMesh pod. AQMesh has been used in all these applications, providing secure, confidential, real-time information to operators, to protect staff and neighbouring communities, and identify sources, mitigating where necessary.

Ports and shipping

Shipping has long been under fire regarding the levels of sulphur in fuel, as well as other air pollutants. AQMesh has been used in various studies which have aimed to identify the sources of pollution around ports, as harbourside operations and nearby traffic movements – inside the port and on roads in the neighbouring area – also create air pollution. Capturing plumes from ships is notoriously difficult but possible, using AQMesh capturing data at 1-minute intervals and wind speed and direction (an integrated AQMesh option), analysed to identify the direction and scale of the source.

Volcanic activity

Volcanoes present another significant source of sulphurous emissions. Five AQMesh pods were installed at and near Keflavik airport in Iceland, monitoring gases produced by the nearby volcano at Fagradalsfjall, including H2S, sulphur dioxide (SO2) and nitrogen dioxide (NO2). The monitoring project was a collaboration between the airport authority, Isavia, and the Icelandic Environment Agency, to ensure good air quality for Isavia staff as well as users of the airport and local residents. Three AQMesh pods were located at Keflavik airport, with two others installed in nearby towns to monitor air quality in the local community, with measurements published on a website.

A 2017 study in Nicaragua, led by the University of Leeds, predated the AQMesh H2S sensor option, focusing on SO2 and particulate matter. The pods, with independent power and communication, were set up to understand how it might be possible to provide early warning to residents of dangerous levels of SO2 and PM.

Monitoring hydrogen sulphides to prevent short-circuits at data centres

H2S in the air – which can come from a number of sources – is a particular risk to information technology, as it can damage copper circuitry. Airborne H2S and SO2 can form a weak acid, which can cause dendrites to form on electronic components, resulting in short-circuits and potential data loss. This risk is growing worldwide, with more compact circuitry increasing the risk of short-circuits, and more data centres being located in areas with higher levels of H2S and SO2 in the air.

H2S attacks copper, forming thin films of metallic sulphides – dendrite whiskers – which speed up corrosion, so some data centre operators monitor H2S outdoors, near air intakes, and internally within UPS rooms to avoid sulphur-induced degradation in power modules. These gaseous contaminants can lead to deterioration of silver solder as well as copper surfaces on computer circuit boards, leading to intermittent and hard errors, caused by either impeding the flow of electricity or forming unintended circuit paths.

Data centres focus on filtration for particles and management of temperature and humidity, but gases in the air may bypass such filtration systems. One method of monitoring for potential corrosion is to expose silver and copper coupons to the air in the server centre and measure corrosion over a month. This is an effective methodology, but the results of the month-long test may arrive too late to prevent damage. Monitoring of the air coming into the building allows real-time notification of elevated levels of H2S and SO2, allowing action to be taken before polluted air enters the data centre.

In 2015 a team from the University of Bonn began monitoring air quality around the Geiranger fjord, Norway. In this pilot study pollutant gases were measured using AQMesh, as well as particulate matter. From 2016 the team installed AQMesh pods at different points around the Fjord. The project is now four years into a long-term programme to quantify pollution, understand the sources and how air pollution is distributed in this complex and sensitive environment.

This project has presented challenges: as well as the harsh climate, which AQMesh is designed to withstand, the mobile phone network – which is critical for communication – also appears to show seasonality, with a reduced network over the winter period. However the AQMesh team has optimised settings remotely to ensure that long-term data capture is ensured.

Geiranger fjord is one of Norway’s most visited tourist sites. In 2005 it was listed as a UNESCO World Heritage Site.

AQMesh is in use around the world and has been deployed across various harbours and ports including the UK, Italy, Norway, Netherlands, Germany and Vietnam. AQMesh can measure up to six pollutant gases, as well as particulate matter, within a single, compact pod. Its flexible platform, wireless infrastructure and range of autonomous power supplies mean it can be easily installed exactly where monitoring is required.

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).

AQMesh has been used in a project at the Port of Kiel, Germany, to measure emissions of nitrous oxides (NOx) and fine particulate matter (PM) around its cruise ship terminal.

This year the port attracted 166 visits by 33 different cruise ships, bringing a record breaking 600,000 visitors into the city. Emissions from the cruise ship terminal and its impact on the local air quality has been in discussion for some time, as the city’s references stations indicate that nitrogen dioxide (NO2) levels regularly exceed the World Health Organisation’s annual mean limit of 40μg/m3.

The joint project with Eurofins and Olfasense, who combined AQMesh air quality monitors with the Ortelium dynamic atlas system, measured and studied levels of NO2 and PM at the cruise ship terminal over several months.

AQMesh pods, supplied by its German distributor Envilyse, measured NO, NO2, O3 alongside PM1, PM2.5 and PM10, as well as relative humidity, temperature and atmospheric pressure. After being co-located with passive samplers at the installation site to provide the greatest degree of accuracy, real time sensor data from the AQMesh pods was fed into Ortelium.

The Ortelium atlas allowed measurements from the AQMesh pod to be visualised in real time and, combined with meteorological data feeds, showed how the emission levels changed during arrival, berthing and departure of the cruise ships.

Data analysis from this study concluded the cruise ships could not be attributed to high levels of NO2. This is similar outcome to a study carried out at a UK airport, which concluded that local traffic was in fact more of an issue than the airport activity.

Plumes from shipping are notoriously difficult to detect and analyse from land, but AQMesh now has a carbon dioxide (CO2) sensor which allows a combustion plume to be detected from elevated CO2 levels. Pollutants can then be evaluated in this context.

AQMesh is in use at a variety of harbours and ports around the world including the UK, Italy, Norway, Netherlands, Germany and Vietnam. The pods can now monitor up to 6 gases using the latest generation of sensors, as well as PM1, PM2.5, PM10 and total particle count (TPC) with a light-scattering optical particle counter.

AQMesh is now able to offer CO2 and H2S within its range of gas options for local air pollution monitoring.

The NDIR CO2 sensor, which can be offered within a single AQMesh pod alongside five other gases out of NO, NO2, O3, CO, SO2 or H2S, as well as PM1, PM2.5, PM10, temperature, pressure and humidity, has been developed to deliver a higher performance than those typically used for indoor air quality monitoring. It has been rigorously tested against Picarro reference equipment, resulting in an R2 value of 0.93. Pod-to-pod correlation of over 20 AQMesh pods has shown R2 values of 0.98 and 0.99, and the sensor has a MAE (mean absolute error) of less than 20ppm.

In addition to monitoring deviations from ambient levels of CO2, elevated CO2 levels can indicate that monitoring is taking place in a combustion plume and levels of other gases can be interpreted accordingly. For example, the ratio of CO2 to the other pollutant gases present can indicate whether those gases were emitted by a local or distant source.

An additional electrochemical sensor has been introduced to offer H2S measurements. After integrating the sensor, measurements have been compared to readings from a Honeywell SPM Flex installed at a sewage treatment site with an R2 value of 0.87 over a measurement range of 0-150ppb. Particularly of interest to the oil and gas industry, in association with the SO2 monitoring already available on AQMesh, it can be used to measure emissions from sour gas and residual emissions from flaring operations.

AQMesh can measure up to 6 pollutant gases in various combinations, as well as particulate matter, humidity, atmospheric pressure and noise in one small, compact easy-to-install unit. There is a range of wireless power options, including lithium battery packs and solar panels, with information sent in near real-time to a secure server via cellular GPRS. Data can be accessed by a secure login or can be streamed via an API connection.

AQMesh pods are in use across the globe in a variety of indoor and outdoor air pollution monitoring applications, and are becoming increasingly popular in smart cities and networks. Pod performance has been proven through extensive testing in worldwide co-location comparison trials with reference equipment, which have delivered impressive and reliable correlation results.