The sulphur-based gases sulphur dioxide (SO2) and hydrogen sulphide (H2S) are known for the impact they can have on metals. AQMesh monitors either or both, from waste processing sites to data centres and volcanic regions.

Two AQMesh pods were installed on a UK wastewater site to measure continuous real-time H2S levels, as the containers housing engines were corroding very quickly. The two pods were mounted in different locations and recorded significant levels of H2S. Peaks of over 400ppb (0.4ppm) were seen in one location, but the high sensitivity of this sensor shows real-time changes at single ppb levels. Readings are typically 15-minute averages, but can be as short as 1-minute, with user-settable alerts available, normally triggered when H2S – or another chosen pollutant – exceeds a set level.

Other applications suffer from high sulphur levels in the air, including landfill, processes which generate biogas – such as palm oil processing – and of course the oil and gas industry, particularly where sour gas is involved. Paper processing and the fertiliser industry also produce oxides of nitrogen (NOx) and sulphur, with one fertiliser plant in Australia using AQMesh to monitor SO2 alongside NOx and ozone (O3).

Another customer in Australia was concerned about the corrosive effects of SO2 from a nearby mining operation and used AQMesh to compare SO2 readings against the corrosion of ‘sacrificial’ metal squares placed on equipment and street furniture.

H2S has a foul and unpleasant odour, which can draw complaints from communities that are near to any facility that is producing it, such as landfill sites. AQMesh is currently installed at several landfill sites in the UK, measuring H2S, total volatile organic compounds (TVOC), carbon dioxide (CO2) and methane (CH4) near their operations and along the site boundaries. Similarly, in the USA, San Diego County Air Pollution Control District (SDAPCD) is using AQMesh to monitor H2S and other pollutants due to toxic waste flowing into the Tijuana River Valley from unregulated wastewater and landfill sites on the Mexican side of the border.

Data centres are also known to be at risk from sulphur in the air. As the largest data centre operators expand into new territories, the local air quality can be different to what they are used to. Whilst back-up generators may cause low levels of sulphur emissions (depending on the fuel used), some industrial areas have consistently or regularly high levels of H2S or SO2. The sensitive copper components that are critical to reliable data management can be affected by airborne sulphur, causing ‘dendrite whiskers’ which cause shorting of components and data errors. Continuous monitoring of the air entering data centre ventilation systems allows the risk to be monitored and managed.

AQMesh was also used in Nicaragua to monitor around volcanic areas, and then around similarly active areas in Iceland. Whilst high levels of SO2 were expected in Nicaragua – that was the point of the project – it was interesting to see what impact what was effectively was airborne sulphuric acid had on the AQMesh pod itself. Although some of the additional security fittings used locally were corroded, the pod coped very well with the harsh conditions.

SO2 and H2S are just two of many measurements that AQMesh pods can be configured to monitor. A single AQMesh system can measure up to 6 gases out of NO, NO2, O3, CO, SO2, H2S, TVOC and CO2, as well as PM, noise and an optional ultrasonic wind speed and direction sensor. Autonomous power can be supplied with the AQMesh smart solar pack and there is a variety of data access options to suit all needs. With wireless communications and remote support, pods can be easily installed anywhere, by anyone.

Contact our experienced team today to find out more about AQMesh and how it can support your industrial monitoring requirements.

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.

Five AQMesh air quality monitoring pods are currently installed around Keflavic airport in Iceland to monitor gases produced by the nearby volcano at Fagradalsfjall, including hydrogen sulphide (H2S), sulphur dioxide (SO2) and nitrogen dioxide (NO2).

The pods were deployed as part of a collaborative project between Isavia, the Icelandic Environment Agency, Suðurnesjabær and AQMesh distributor for Iceland, Verkfræðistofan Vista, in line with Isavia’s sustainability strategy and to ensure good air quality for Isavia staff as well as users of the airport and local residents.

Sveinbjörn Indriðason, CEO of Isavia, says “It is very important for us to be able to have a good overview of air quality at Keflavík Airport and these new meters make our work easier. Good air quality is important to our staff, guests and the airport’s local environment. The investment in the new meters will therefore also result in increased accuracy in measurements in Reykjanes and in the Environment Agency’s measurement network.”

Three AQMesh pods are located at Keflavic airport, with two others installed in the nearby towns of Sandgerði and in Garður to monitor air quality in the local community. Data from the AQMesh pods will be made available to the public on the Environment Agency’s website, using API to integrate air quality readings into a real-time colour-coded map of the local area.

“We are very pleased with the collaboration with Isavia in setting up air quality meters that will ensure good air circulation for Isavia employees, tourists and residents of Reykjanes. The technology has advanced and it is now much easier to have measurements that are shown in real time. We congratulate Isavia on the meters.” says Heiðar Karlsson, CEO of Verkfræðistofan Vista.

He adds “The reason we picked AQMesh as the supplier for this project was for the good accuracy of the pods and their ease to setup and operate. AQMesh have proven that they are able to meet our needs in terms of quick response and technical know-how when it comes to delivering accurate and reliable air quality measurements in a demanding environment.”

AQMesh is currently in use in Nicaragua, monitoring air quality in communities living near Masaya volcano. The six AQMesh pods have been used to show variations in volcanogenic SO2 and PM levels at different times and at different locations across the area.

The pods, which have independent power and communications so they can be mounted where required, were installed in March 2017 as part of a research project funded by the Global Challenges Research Fund: Unseen but not unfelt: resilience to persistent volcanic emissions (UNRESP). The project is led by the University of Leeds and is a multi-partner collaboration of several universities in the UK and Nicaragua, as well as Nicaragua’s natural hazards observatory INETER and the Icelandic Met Office.

The Global Challenges Research Fund supports projects focusing on challenges faced by developing countries, aiming to build resilience to natural and anthropogenic hazards. The aim of UNRESP project is to devise an early warning system for dangerously high levels of air pollution, specifically SO2 and particulate matter. As this is a 12-month foundation phase project, the data are not currently being made public but will be put in the hands of local authorities and other stakeholders when the warning system is refined. AQMesh readings are being compared to predictions from a pollution dispersion model, CALPUFF, which requires relatively little computing power. The CALPUFF model has been successfully used for air pollution forecasting at other volcanic sites, such as a recent eruption in Iceland which did not produce ash but emitted twice as much SO2 as all European Union countries combined and caused repeated air pollution in Iceland for 6 months.

“Air pollution is a chronic and serious hazard affecting many developing countries, but there is generally very limited capability to monitor and mitigate it. AQMesh provided us with an opportunity to install the first AQ monitoring system in Nicaragua – the pods are very cost-effective which is of utmost importance for the local setting, yet they provide data that are of high quality. Real-time data on the ground is vital for quantifying and understanding the duration, peak concentration and frequency of high air pollution episodes, which are factors that directly impact human health”, commented Dr. Evgenia Ilyinskaya who is leading the project. The UNRESP team started by hiring five pods for three months via UK distributor, Air Monitors Ltd. as well as purchasing one AQMesh pod for long-term observations. The pod rental has been extended for another three months and the practicality of long-term use of this sort of equipment is being evaluated, including the use of rechargeable batteries or solar power. The team is working closely with local communities and such stakeholders taking custody of the equipment intended to protect their own community mitigates against some risks, such as theft or damage.

Although there is no reference station at the site, diffusion tubes have been used to take measurements which can be compared to the 15-minute average, real-time readings from AQMesh. Whilst EU air quality standards focus on the short-term high concentrations typical of SO2 from an industrial source the UNRESP team is trying to understand the impact of long-term elevated SO2 on the population. Having SO2 measurements with high time and spatial resolution is critical for this and the plan is to potentially create an alert for accumulated concentration of pollutants.

The draft proposal for a follow-on project at the site states the collaboration with AQMesh identified ways of improving the equipment for monitoring volcanogenic pollution, which tends to be much more corrosive than ‘typical’ urban pollution. Dr. Evgenia Ilyinskaya commented, “the AQMesh equipment is extremely cost-effective while providing data quality comparable with EU-certified monitoring. One AQMET station was purchased during the UNRESP foundation phase and it will remain in Nicaragua to form part of the permanent AQ network.”