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.

A good quality small sensor air quality monitoring system should last 10 years or more, and of course certified monitoring stations (reference, FRM, FEM) should last much longer.

Looking at the many small sensor systems used for outdoor air pollution monitoring, the question may be ‘how long will my air quality monitor work between services’? The best systems operate for two years between sensor changes, and sensors should be low cost and locally replaceable, with no need to return equipment to the manufacturer for service or calibration.

Whether considering the operational life of the product or time between each service, it is important not to assume that all products are the same. Some systems are not designed to work for more than a year or so, which might meet the needs of a shorter project and budget, but it may cause a series of unscheduled equipment failures in the middle of an important monitoring period. So, it’s worth asking for examples of long-running projects where long-term operation of the system can be proven.

Any intervention during the operation of an air quality system costs money, even if it is ‘only’ the time and effort of local teams, so this must be minimised. Scheduled service work is undesirable, but unscheduled maintenance demands are worse. AQMesh sensor replacements are based on carefully calculated duty cycles – balancing initial costs against expected life and product performance – and the pods have been proven over years of operation around the world.

Of course, any equipment will be affected by operating conditions but small microsensor users should not expect their system to fail prematurely in harsh conditions. ‘Fit for purpose’ systems will be proven in intense heat, heavy rain, strong winds, freezing temperatures and snowfall: an expected 10-year lifetime should not just apply to easy conditions.

Having said all that, product lifetime will always be extended by careful use and following the manufacturer’s advice. The AQMesh user manual is now supplemented by a range of remote diagnostic tools, which detect signs of product ‘distress’, such as lower voltage from a dirty solar panel or potentially blocked air sample path.

Even if few air quality monitoring projects extend to 10 years, a product which is designed to last that long is fit to be used in a series of projects and can be upgraded or traded in, as requirements change.

Here at AQMesh we have a number of long-standing users who re-use their pods for new projects, and we are happy to discuss how we can help you with your own air quality monitoring requirements.

“How many air quality monitors do I need?” is a question we regularly hear, and the easy responses – “it depends”, “how big is your budget?” – are not very helpful.

To give a better idea, it will depend on all these factors:-

Which pollutants you want to measure

Some pollutants are mixed better / are more homogeneous / more background in ambient air, such as PM2.5 and O3. Others are less so, and can be affected by a local source, like NO. Background pollutants can be measured with fewer measurement points than those which will vary greatly over short distances. For example, O3 may range between 50ppb and 60ppb across a city, but NO could vary from 0ppb to 1,000ppb within just 100m.

Your analysis capability

If you have the resources or skills to carry out detailed analysis, you will get more information out of fewer measurement points. For example, if using wind speed and direction data alongside air quality readings, you can look at an area in terms of pollution sources and areas potentially affected by air quality. The resulting plots and mapping allow reading levels to be visualised across space. Taking it further, measurement points can be linked to emissions inventories and modelling can fill the gaps to give an estimated reading for every geographical point. The more measurement points, the more accurate the estimates are likely to be. Additionally, some analysis techniques – such as long distance scaling or network calibration – require a minimum number of measurement points in order to work, which will therefore determine how many pods you might need. As an example, the long distance scaling method offered by AQMesh requires a minimum of 6 different locations.

The area you’re monitoring in

Multiple pollution sources (think busy city vs. a factory in open countryside) create a more complex air quality situation, as do canyons (naturally confined air corridors or streets between high buildings). A single source within an open environment could achieve a lot with just one pod upwind and one downwind, but a city environment means that NO or NO2 readings could be massively different just other sides of a road junction.

Local conditions

If your air quality monitoring location is generally windy you will have to work harder (install more measurement points to pick up plumes) to capture pollutant bursts before they are swept away.

Environmental justice

We have seen customers distribute pods based on one per ZIP code, to achieve fairness to local communities. This is a good idea in itself, but a ZIP code can include a wide range of pollution levels so all the factors about choosing a precise monitoring point still apply.

And, of course, budget!

Seriously, small sensor systems are described as monitoring ‘hyperlocal’ air quality for a reason and even the densest networks will be leaving some gaps where air quality variation is not recorded. So, measurement points can be added infinitely – air quality mapping of an area will improve in accuracy, but there are obviously diminishing returns.

Because, even after all this, “it depends”, just talk to us about your air quality monitoring requirements and we will be more than happy to share our recommendations and give you a more helpful answer to “how many air quality monitors will I need?”

Hydrogen sulphide around and – even worse – escaping from a site can be a problem. As well as presenting a safety concern, H2S is often a nuisance odour.

Detection and quantification at very low levels allows the source of the gas to be tracked down and addressed, or real-time continuous readings from around the site can demonstrate compliance with local restrictions. 

H2S monitoring options 

The AQMesh H2S sensor option measures the gas at single figure ppb levels, well below the level at which an odour can be detected (about 100ppb / 0.1ppm), giving ‘pre-odour’ warning or surveillance. Exceedance alerts can be set up at user-defined levels. 

H2S is one of many AQMesh sensor options, including NOx, SOx and particulate matter or dust. The pods are small and, with solar power and mobile communications, can be installed very flexibly and quickly at appropriate locations. Sensor output is transmitted to the secure cloud AQMesh server, where confidential processed readings are available by secure web app login or API.  

Measuring hydrogen sulphide in harsh conditions 

AQMesh has been used successfully to monitor H2S across a wide range of applications and climates, including fugitive emissions along site boundaries, and projects in New Zealand, South Africa, Iceland and UK. Field testing of the sensor was initially carried out in the sludge lanes of a wastewater treatment plant, and it has since been used in oil and gas, volcanic emissions, shipping ports and biorefineries. Most recently, AQMesh has been used to monitor H2S – and other – emissions from toxic landfill sludge and wastewater spilling into a river in San Diego, USA, and a UK wastewater treatment plant is measuring H2S to protect CHP engine infrastructure.  

H2S monitoring at data centres  

We have seen a huge uptake from data centres, whether to comply with local regulations about back-up generator use, or to guard against the potential damage to copper circuitry from this corrosive airborne pollutant.  

Fugitive hydrogen sulphide emissions 

Other industrial processes where monitoring H2S in real-time can be beneficial are lime manufacture and the pulp and paper industry, where NO2, SO2, VOCs and dust can also be an issue. Some users add the AQMesh CO2 sensor to their specification as it can be used in combination with other gas measurements to be an indicator of fugitive landfill emissions. 

Real-time data for landfills, oil & gas operators and industrial processors  

Monitoring along the boundary of landfills, oil & gas plants or other industrial processing sites can offer real-time information to operators to ensure that staff and any nearby communities are not affected by emissions. AQMesh pods can be deployed along fencelines to monitor not only H2S but SO2, CO2, and TVOCs, including ethylene oxide, which can all be pollutants of concern. Analysis of pollutants in combination with wind speed and direction information (AQMesh offers an integrated ultrasonic wind sensor) allows pollution sources to be identified. This is particularly helpful where there are several neighbouring sites – which one could be the polluter? 

All AQMesh pods are built to order with a standard lead time of 2 weeks and every user benefits from remote support for the life of the pod, wherever they are in the world. 

For more information on using AQMesh air quality monitors for H2S monitoring and more, contact our experienced team today. 

Mining sites are generally dusty places – but how dusty? Is the health of workers at risk, could local communities be affected or operations compromised? As well as high levels of particulate matter, mining facilities may also generate pollution from other activities, such as engines producing oxides of sulphur or nitrogen.

To add potential complication, there may be other sources of the same pollutants in the same area, as well as vulnerable communities. A reliable air quality monitoring system can provide a clear and confidential picture of air pollutant levels at a mining site. Continuous pollutant readings from across and around a project offer real insights to inform operations.

A practical air quality monitoring tool that’s up to the job

AQMesh pods can be installed – with no training – in ten minutes, as they come with simple post fittings and have autonomous communication, using the local phone network to transmit data to a cloud server. Whilst direct power supply is an option, the smart solar pack offers reliable 12-month power in most locations, and is equally easy to set up. 

Mines are notoriously tough sites, with high dust levels, use of heavy machinery and dust suppression spraying. AQMesh has been designed and proven to withstand not only these challenges but the worst that nature can present. Long-term monitoring around mining facilities from Saudi Arabia and Australia to Sweden and Canada has demonstrated robust performance in hot and dry to freezing conditions. 

Meaningful air quality information to support operations 

A real-time view of pollution, which can be related to operational activities and events, can provide unique insights into how your operations are – or are not – impacting local air quality. Identifying peaks of pollutants by exact time of day and location brings some hard facts into any question of air quality levels around the site or over the boundary towards neighbouring communities.  

As well as creating a valuable historical record of measured pollution levels, near real-time readings can be used to trigger exceedance alerts, evaluate dust mitigation measures or provide data for compliance to local environmental standards. Measurement accuracy is underlined by indicative MCERTS certification for PM2.5 and PM10. 

Scope to go further 

Whilst even a single pod can answer many questions about air pollution around a mining facility, it is possible to set up a larger network of pods around a site. AQMesh can also be used alongside other measurement technologies, including passive sampling, bag samples or reference / equivalence method technology, to provide cross-checking and traceability. Baseline levels can be compared to operational air pollution profiles, and the AQMesh ultrasonic wind sensor can be used for complex site analysis, and even as the basis for modelling. 

AQMesh has been developed to meet the challenges of long-term use in mining applications and users include the biggest names in global mining. Mining applications include copper, lithium, phosphate, nickel, cobalt, nitrates with locations from Australia to Zambia. AQMesh offers a robust, autonomous network that can be a ‘sentry’ for years, with minimal maintenance/cost. 

Communities and industry are monitoring air quality around the same areas, so they both want the same thing, right? Er, no, not really ..

Even though both types of AQMesh user may measure the same pollutants using the same instrument, their objectives and needs are often different. The community users we deal with – mostly in the UK and USA, but plenty of other places too – tend to be more interested in identifying pollution events and relating that to what they are experiencing. The first step is a sort of validation of what they believe to be happening all around them. This is not to say that the review of data is selective or unscientific, it’s just experience-focused. For example, school monitoring projects are generally focused on identifying periods of elevated air pollution outside and around the school at different times in the school day and finding the cause / source.

On the other hand, air quality monitoring around communities by the industries that may be the source of the pollution takes a different approach. Our industrial customers – from oil and gas, construction, mining, landfill and other sectors – want accurate air pollution measurements to demonstrate that they are within compliance of local environmental regulations. Another aspect is that there is often more than one potential source of pollution in an area so an industrial AQMesh user may be keen to understand more about what pollution is coming from where (and hopefully proving that a neighbouring facility is causing the issue, not them). Accurate wind data is required to carry out such source apportionment analysis. AQMesh offer a wind speed and direction sensor option and normally only one pod in an area needs to be gathering this information.

Whilst communities and industries may have slightly different air pollution monitoring objectives, they recognise the benefit of using the same instruments, so the data is comparable. A version of this desire to be able to make meaningful comparisons is where government monitoring uses a particular type of equipment and the potential industrial polluters being monitored choose to use the same technology. For example, a community in Texas, USA, installed AQMesh pods outside suspected polluters, so the industrial facility (or rather a consultancy they hired) bought AQMesh systems to monitor themselves. This helps to build trust that data collection and analysis will be done correctly and in an unbiased manner. Another factor bringing all parties together is when there is a natural cause for the pollution affecting people, such as volcanoes (see our news items about airport and community in Iceland) and wildfires.

In the USA, industrial companies are aware that use of uncertified equipment – other than FRM / FEM – means they cannot be obliged to report on data. This creates a ‘safe space’ for potential polluters to understand the air quality around their operations and their impact on it, ahead of compliance demands.

And then there are data centres, where the focus is not on the potential for pollutants to harm people but infrastructure. Hydrogen sulphide monitoring can warn of potential damage to sensitive copper circuits and HVAC maintenance intervals can be managed by monitoring of PM levels, helping to prevent machinery failures.

So, whilst different customers are all using the same air quality monitoring systems and measuring the same pollutants, the reasons driving the project may be entirely different. Either way, our experienced team can support a range of objectives and help interpret your data with meaningful context.

Air quality monitoring stations have been used by the Scottish Environment Protection Agency (SEPA) to form a new air quality monitoring network around the Mossmorran Complex near Cowdenbeath and Lochgelly, Fife.

The network of 8 AQMesh pods was deployed in addition to a fixed air quality monitoring station to help address the concerns of the local community about the impact of operational activity at ExxonMobil Chemical Limited Natural Liquids Plant and Fife Ethylene Plant in Fife, Scotland. Both plants use flaring processes to burn off excess gas, and SEPA set out a series of regulations aimed at reducing the amount – and impact – of flaring, as well as being able to provide local residents with accurate, real-time information about pollution levels in the wider community.

Commenting on using the AQMesh pods, SEPA have stated that “these analysers are easier to locate than the reference analysers due to their size and power requirements and can be installed in more accessible locations. They are useful in assessing short-term trends in pollutants; provide greater geographical coverage both up and down wind of the site; and monitor for a wider range of pollutants.”

So far, all the pods and fixed station continue to show that there have been no breaches of any air quality standards since monitoring began.

The quality of the data produced by the AQMesh pods at the Mossmorran facility has been optimised using a proprietary network calibration method known as ‘long distance scaling’, which identifies and separates hyperlocal events from individual pods in order to determine the common pollutant trends seen on each pod in the network. These data trends are then directly comparable on each pod, showing the background/baseline pollution levels across the network and can also be used to provide calibration – or scaling – factors that can be applied to each pod. The method is similar to that developed by Professor Rod Jones of the University of Cambridge, which was used for calibration and quality control of 100 AQMesh pods in the Breathe London pilot.

For more information about SEPA’s air quality monitoring network at Mossmorran, or about AQMesh, contact us today.

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.

Requests to measure hydrogen sulphide (H2S) in ambient air at unthinkably high levels seem to be at odds with our efforts to detect and report single-figure parts per billion H2S emissions. So, why are we asked for such high ranges?

We think this may be explained by operators who are used to measuring high concentration in a gas stream – typically biogas or industrial – and then simply transferring the range across when looking at fenceline monitoring. It’s great to see the growing interest in monitoring fugitive emissions at site boundaries – including H2S – but we need to dial back the gas range expected when looking at ambient pollution.

H2S sensors for gas stream measurement are offered at parts per million ranges from 0-50ppm to 0-10,000ppm. Bear in mind that US Department of Labor guidelines say that H2S odour becomes offensive at only 3-5ppm, with prolonged exposure causing headaches, nausea and insomnia, and causes “nearly instant death” at 1,000-2,000pm. Dilution of any emission in swirling ambient air means that parts per million measurements are inappropriate, and even significant H2S leaks usually register peaks of just a few parts per billion by the time gas has reached the fence line.

That’s why the AQMesh sensor measures from 0-10,000ppb (0-10ppm), with a limit of detection of less than 1ppb. Measuring at such low levels means operators can pick up emissions much earlier and much further away from the source than would be the case with the higher range sensor typically used for measuring the gas stream. Picking up a low level at a suitable point on the industrial boundary should avoid dangerous levels of H2S building up near the source.

Monitoring in ambient air is gentler on sensors, too, so if you are used to sensor poisoning and condensate problems, that benefit does offset the ‘needle in a haystack’ challenge of picking up fugitive H2S emissions. With the potential to move an AQMesh pod from location to location, and add a wind speed and direction sensor to help with source apportionment, it is very satisfying to support our users doing just that.

Each time we think we have found a spectacularly remote air quality 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.