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Gravimetric Air Sampling

Air Sampler Head

Air quality assessments help to quantitatively evaluate the fraction of harmful material in the air. In many industries, this may be a legal requirement to ensure standards are being met or to determine the effectiveness of control strategies.That’s why Air Quality Sensors / Air Quality Monitors are used

Protect the environment

Employers must take all steps possible to protect workers from exposure to health-harming substances. Any breach of safety regulations can have a major impact on labour effectiveness and places the employer at risk of grave legal consequences. Most government agencies have established ceiling values and guidance limits for a range of harmful gases, vapours, radionuclides and dusts. In the UK, a list of Workplace Exposure Limits (WELs) and occupational standards is downloadable for free on the HSE website (E40/2005). This document is legally binding; non-compliance will result in major penalties.

Gravimetric air sampling is thought to be the most accurate method of determining particulate mass concentration, as they are capable of sampling at the very lowest detection limits. A sample is taken by drawing a measured volume of air through a collection substrate, which is then sent for further analysis. When sampling gravimetrically, the airborne concentration of a particular substance is calculated by assessing the analytical result and the volume of air sampled.

Types of Gravimetric Air Sampler

The type of air sampler used depends on the size of the area and the duration of the sample. Fixed-point samplers (also known as area samplers) have high flow rates, meaning large volumes of air can be sampled in a short space of time. These are useful for pinpointing the source of contamination and for assessing the effectiveness of control measures.

To monitor personal exposure, a smaller, wearable sampler may be used. These are attached to the operator, and a sample is taken during normal working activity. The sampling head is located in the worker’s breathing zone in order to measure how much particulate matter is inhaled.

For both types of sampling, different filter paper can be used depending on the test parameters.

Although real-time monitors can be extremely useful for initial assessments, they may not be sensitive enough to detect background levels when the concentration of a pollutant is very low.

Munro Instruments specialises in the manufacture of high-quality environmental monitoring equipment. Our comprehensive range of air samplers cater for all environmental and health-and-safety requirements and can be found in nuclear, construction, transport and agricultural facilities around the world.

Gravimetric Air Sampling

Contact us or visit our product pages for more information.

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Farming and Pollution


The rise of large-scale factory farms in recent years has raised questions about their impact on surrounding areas. What pollutants are they putting into the air?

Researchers from the Earth Institute at Columbia University found that where farm emissions combine with industrial waste and vehicle pollution this leads to the creation of harmful aerosols.

Particulate Matter

The study discovered that industrial emissions release large quantities of nitrogen oxides and sulphates. These compounds combine with chemicals, mainly ammonia gas from livestock waste and fertiliser, to create dangerous fine particulate matter known as PM2.5. Inhaling PM2.5 can lead to respiratory problems, bronchitis, a decline in lung function and organic dust toxic syndrome. In some cases smaller particulates can be absorbed into the blood stream and go on to affect the major organs.

In one experiment, researchers from Texas Tech placed air samplers 10 to 30 metres upwind and downwind from animal farms between the months of October and March. 60% of the downwind samples and 30% on the upwind samples contained tetracycline antibiotics from airborne manure particles.

In recent years the factory farming industry has proposed “good neighbour” policies to reduce the sights, sounds and smells of modern factory farming and to prevent/reduce water pollution. This has been difficult to sustain due to the rising costs of complying with environmental regulation and animal welfare concerns. More farm waste is inevitable.

However, factory farm emissions must combine with industrial pollutants to make hazardous aerosols and particulate matter. Some organisations have argued that the tighter regulations on industrial pollutants are enforced, the more popular clean sources of energy will become. And if fossil fuel emissions are drastically reduced, farm emissions will be starved of the necessary compounds to become dangerous aerosols. If future industrial emissions go down, farm-produced ammonia will float high up in to earth’s troposphere. There, lightning and other natural processes could potentially create fine particulates, but most of these particles would be trapped by raindrops and removed harmlessly.

All this said, vast quantities of animal waste and excess fertilisers wash off industrial fields each year into the surrounding environment, polluting land and water and disrupting ecosystems. And sulphates, a by-product of industrial processes, have been credited with reflecting solar radiation thereby reducing ongoing global warming caused by other fossil-fuel emissions. But, as stated by Susanne Bauer, an atmospheric scientist at Columbia: “It’s all pollution, but in some sense, some of it is good. We must decide: do we want a small cooling effect, or do we want clean air?”.

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NO₂ in London


London has some of the highest levels of street pollution in the world. Oxford Street, a busy shopping zone, is one of London’s worst affected areas, with high concentrations of nitrogen dioxide (NO2) recorded. This pollutant is produced when fossil fuels are burned. Oxford Street is particularly badly affected owing to the volume of traffic on the road.

NO2, as a concentration, is measured in micrograms per cubic metre of air (µg/m³). A concentration of 1 µg/m³ means that one cubic metre of air contains one microgram of nitrogen dioxide. In a recent pollution report by Kings College London, Oxford Street was found to have an average amount of 143 micrograms of NO2 per cubic metre. The report also states that there were 1,532 hours during the year when that figure was above 200 micrograms. According to the World Health Organisation, the average level of NO2 should not exceed 200 micrograms more than 18 times a year.

The prevalence of NO2 is partly attributable to the fact that buses in London are using diesel oxidation catalysts and particle filters. In order to burn off the black soot from diesel engine emissions, exhaust gases need to reach temperatures in excess of 500°C; however, NO2 can be used to burn these sooty particles at a much lower temperature (around 200°C). As a consequence, higher amounts of NO2 are released into the atmosphere.

Ambient air monitoring is essential in large, busy cities, as high levels of pollution can cause respiratory problems and inflammation of the lungs. Transport for London (TfL) has now introduced pollution alerts, which can be found at bus stops and train stations.

If you would like further information about any of our Air Quality products, please get in touch via email ( or phone (+44 (0) 20 8551 7000).

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Introduction to Air Sampling

Air Sampler Head

Air Sampling involves drawing a known volume of air through a filter, trapping the contaminants and measuring the amount of contaminant captured. Introduction to Air Sampling

The results are usually expressed as a concentration, calculated by dividing the volume of air by the amount of contaminant captured. To calculate the volume of air, you multiply the flow rate (usually expressed in Litres Per Minute) by the duration of the sample. For this reason, the air sampler must be carefully calibrated before use to ensure the flow rate is correct. Often, multiple samples are required to provide a better understanding of the environment.

There are many different devices which can be used for air sampling:

  • Static Area samplers generally have high flow rates, meaning large volumes of air can be sampled in a short space of time. These are useful for pinpointing the source of contamination and for assessing the effectiveness of control measures.
  • Personal Air Samplers are smaller in size and have a lower flow rate. They are attached to the operator, and a sample is taken during normal working activity (usually over an 8-hour period). The sampling head is located in the worker’s breathing zone to measure how much particulate matter is inhaled.

In some industries these instruments are a legal requirement to detect the concentration of harmful airborne substances in a worker’s breathing area. These include aerosols, dusts, fumes, smokes and mists. All are a danger to health, as small particles can settle on the lining of the lungs and cause respiratory problems.

By taking air samples, employers can protect their workforce from exposure to airborne contaminants.

Introduction to Air Sampling

If you would like information on about any of air sampler products, please get in touch via email ( or by phone (+44 (0) 20 8551 7000).

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Whose pollution anyway?

Santiago smog

The weather impacts air quality. It comes as no surprise, then, that many of the world’s most polluted cities are awkwardly situated from climatic perspective. In Santiago, Chile, where air pollution regularly exceeds critical levels, scanty rain and low wind speeds prevent atmospheric mixing from taking place, causing a build-up of smog. The city’s striking mountainous backdrop serves only to exacerbate the situation.

Wintertime in pollution-prone cities can be particularly problematic. When nights are long and the sun much lower in the sky, ground temperature often falls below that of the atmosphere, making vertical air movement (convection) more difficult. Temperature inversions of this nature create warm, impenetrable layers of air that trap pollutants at ground level. This is a common occurrence in Delhi and Beijing, two heavily contaminated cities.

the effect of weather on air pollution

Keeping in mind the effect of weather on air pollution, we find that there is another issue at stake – one of transnational political significance. The wind may help disperse contaminants, but it also carries domestic emissions across international borders. Although no modern nation is entirely blameless, China, with its reliance on dirty fuels and heavy industry, is a serial offender. Japan and South Korea have long borne the brunt of China’s accidental airborne attacks. It is even thought that some air quality violations in the US are directly attributable to emissions originating in Asia [1]. A similar state of affairs exists between the US and Canada. But despite sharing each other’s emissions, an Air Quality Agreement (established in 1991) is in place to tackle transboundary air issues. Bilateral agreements such as this are vital for effective management of cross-border pollution. Although responsibility resides with the producer, collaborative initiatives are needed to prevent hostility.

Air Quality Monitoring Strategies

Despite being a largely anthropogenic phenomenon, bad air is influenced by a number of factors outside of human control. Regardless, cross-border pollution produces a negative externality and may be viewed as a violation on the part of the producer. The observation of meteorological parameters, such as wind speed and direction, relative humidity and temperature, should be integrated into air quality monitoring strategies, as this will give us a better chance at understanding it.

Whose pollution anyway?

[1] ‘China Exports Pollution to the U.S., Study Finds’, New York Times (20 January 2014)

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Low Emission Zones

Heavy Traffic

Poor air quality is known to be the most significant environmental cause of premature death in the EU. This disturbing fact also extends to many other countries around the world. Initiatives to combat this issue are therefore a priority for many governments. The implementation of a Low Emission Zone (LEZ) is one such initiative. LEZs aim to improve air quality by encouraging the adoption of cleaner vehicles.

Over the last decade there has been an explosion in the number of LEZs within the EU. This has mainly been in response to the EU Clean Air Directive (2005).  This sets maximum allowable limits on certain pollutants within specified spatial zones. If violated, local governments are required to produce a Clean Air Action Plan, which must consist of a number of pollution-reducing measures.  The most radical of these measures is the LEZ. In Europe alone, almost 200 LEZs have been, or are being, introduced.  The finer details of each scheme vary, but most deter polluting vehicles by levying a charge on vehicles that do not comply with certain green standards.

LEZs are of vital importance in controlling the devastating human, health and environmental cost of poor air quality. Of particular concern are particulate pollutants (PM10 and PM2.5). The number of EU deaths attributable to PM10 is 348,000 annually. The LEZs address this pressing issue by reducing emissions of particulate matter in densely populated areas.

Key Examples of Low Emission Zones


Germany has been particularly active with the introduction of LEZs to 47 cities. Every vehicle in the country is now required to display a coloured windscreen sticker indicating its pollution (PM10) class.  Depending upon the colour of the sticker, a vehicle may be banned from driving into an LEZ unless a charge has been paid.

United Kingdom

Introduced in 2008, London is home to the largest LEZ in the world. Covering most of Greater London, non-compliant vehicles are required to pay a daily charge of £100-200 to enter the zone.  The scheme mainly targets commercial vehicles such as lorries, vans and coaches and therefore affects businesses most.

The Mayor of London has recently confirmed plans to enhance London’s air quality measures with the introduction of an Ultra Low Emission Zone (ULEZ). This will require every vehicle entering central London to comply with given emissions standards. Non-compliant vehicles will be expected to pay a charge.

The Future of Low Emission Zones

Air quality continues to challenge governments around the world. LEZs are an effective way of combatting the problem, and we expect them to become increasingly commonplace.


European Commission Air Quality Website:
Watkiss, Pye & Holland (2005) ‘CAFE CBA: baseline analysis 2000-2020’ Report to the European Commission DG Environment, Brussels
Wolff (2013): ‘Keep Your Clunker in the Suburb: Low Emission Zones and the Adoption of Green Vehicles’, The Economic Journal 124 (August)

Low Emission Zones

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Energy Security

Energy Security

No longer are renewables the sole preserve of the environmentally minded. Technological advances have improved efficiency and reduced costs, helping to restore faith in the clean energy market. For many, investment in this sector has proved extremely profitable. Countries and corporations are seeking new ways to innovate and rationalize without having to mine, frack or burn.

From Nepal to Spain, Denmark to Peru, renewables are helping enliven economies, increase productivity and save lives. Even China, the world’s naughtiest polluter, has recognised their potential, having pumped US$56 billion into wind and solar projects in 2013 – more than all of Europe combined (source: The Economist). Whilst not to undermine their green agenda, business-savvy China is well aware that continued reliance on fossil fuels is unsustainable. Environmental degradation is poisoning the economy as well as its people, making China less attractive to prospective investors. Added to that is the constant fluctuation of fossil fuel prices. It would seem the modern affinity with renewables is related, at least in part, to the search for greater energy security. As the world’s population grows, so too does the demand for electricity. It is high time we explored some of the world’s other great energy sources.

But there is another problem: the world is not yet equipped to deal with such high demand. Billions of people, mostly in remote, rural locations (Sub-Saharan Africa being a prime example), are still without an adequate supply of electricity. Grid power is often inaccessible or simply too expensive. The implications? Work and study are limited to daylight hours (reducing productivity); crimes are easier to commit; food hygiene is a constant challenge because of inadequate (or non-existent) refrigeration; and hospitals are severely limited in scope. Rural poverty often precludes the possibility of electrification, which affects quality of life and, in turn, results in a whole lot of untapped human potential.

Schemes to ‘electrify’ rural areas are by no means a new phenomenon. Major progress has already been made using off-grid photovoltaic and wind systems. Once prohibitively expensive, microgeneration technologies are becoming more accessible, helping to empower (literally) individuals and communities worldwide. Night-time light makes for a safer, more pleasant and productive atmosphere; air quality improves because of reduced reliance on paraffin (kerosene); food can be refrigerated; businesses set up; and difficult agricultural processes mechanized. Where grid power is not a possibility, microgeneration using renewables is a genuine, sustainable solution.

And even where advanced grid networks do exist, basic microgeneration technology enables households and businesses to supplement their existing supply, reducing costs and creating a stronger, more reliable and efficient source of electricity.

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Corporate Citizenship


Good businesses ensure that workers are happy and healthy – productivity depends on it. Low satisfaction, medical complaints and absenteeism affect employee performance and reduce output. Where legislation exists protecting workers’ health and well-being (as it does in much of the world), it should be viewed not as a minimum legal requirement but as a means to securing the future success and growth of the company. Good corporate citizenship helps businesses to maximize the value of their workforce and make more efficient use of resources.

One parameter that is often overlooked is the impact of air quality on worker experience. Given that most workers’ daily lives are spent in a single location, this is certainly not something that should be ignored. Factories, warehouses, office blocks and shops are all susceptible to airborne nasties – either as a by-product of day-to-day business activity or as a consequence of a building’s infrastructure or location. If neglected, this can have a deleterious effect on the workforce. A meta-analysis by the Guardian newspaper found that poor air quality lowered performance by up to 10% on measures such as typing speed. Ventilated work spaces were found to have 35% fewer instances of sick leave [1].

Fortunately, simple steps can be taken to mitigate the problem. Below are a small selection of tips and suggestions:

  • Every workspace must be well-ventilated to allow the change and circulation of fresh air. If this is not possible, consider installing an air purification system.
  • The temperature and humidity should be closely monitored to prevent the spread bacteria and spores.
  • Floors and surfaces should be kept clean and dust-free. Use only non-toxic cleaning agents.
  • Machinery should be kept clean and up-to-date. This includes printers and photocopiers, as these give off ozone, an odourless gas known to cause headaches, skin irritation and breathing difficulties.
  • Include plants in your workspace. These help absorb VOCs.

Given the size and ubiquity of airborne particles, there is no sure-fire way of controlling what we breathe in. However, regular monitoring will help identify risk zones and enable the implementation of relief measures.

By monitoring  air quality and other related parameters in-house, not only will businesses save money, it will allow them to develop responsibly and create new metrics to measure change and progress.

[1] ‘Office buildings are key to workers’ health, wellbeing and productivity’, Guardian (24 September 2014)

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Embassy Monitoring

global warming

For a little under a week Chai Jing’s Under the Dome eluded censors. The controversial documentary, which explores China’s air pollution crisis, amassed hundreds of millions of views across the country. Speaking directly to a Chinese audience, Chai Jing confronts some uncomfortable truths. She combines shocking imagery, statistical data and the touching story of her own daughter – who was diagnosed with a tumour in utero– to denounce China’s appalling air quality record. Despite praising the video, using it to reaffirm their ‘War on Pollution’, the Chinese government soon banished it from the internet. Chai had successfully reframed the air quality debate from a public health perspective, prompting something of a national awakening. For the Chinese government this brought with it the threat of subversion.

Meanwhile in the UK, #SmogAlert has been dominating Twitter feeds. Last week the country was enveloped in thick, toxic smog, as a cloud of Saharan dust made its way across Europe and mingled with some of our own home-grown emissions. Public health authorities issued warnings urging people to stay indoors, clearly showing, as in Chai Jing’s Under the Dome, that if action is not taken voluntarily, air pollution will change the way we live permanently.

If governments withhold, falsify or manipulate air quality data (as China and the UK have both been accused of doing), citizens’ health and well-being are severely endangered. Providing accurate and timely air quality broadcasts assists the public in making informed and meaningful decisions about where not to go and how best to avoid the health problems associated with air pollution. It also raises awareness and aids mitigation efforts.

A scheme by the US government has succeeded in doing just that. By installing air quality monitors in its embassies and consulates, and making the readings publicly available via Twitter and other means, the US is improving data coverage in underrepresented areas. In turn, this is helping locals make informed lifestyle choices to assuage the threat of air pollution. It also promotes data transparency and creates a pool of analysable data for future modelling.

Although still in its infancy, the scheme has produced some remarkable results. In China, information disparities sparked outrage amongst Chinese environmental officials. The programme was declared illegal, as it contravened official readings; but, even so, it soon prompted the Chinese government to take action. Five years after its inception, 500 PM2.5 stations had been set up in over 70 cities, and billions of dollars were pledged to clean China’s air [1]. The US is piloting similar projects in India and Mongolia.

By promoting the free flow of air quality data, the embassy-monitoring initiative has helped influence policymakers at both local and national levels. Given the enormous data scarcity in much of the world (particularly in Africa), it seems highly appropriate that other countries follow suit to help us overcome this global problem. After all, you cannot control what you do not measure.

[1] ‘How the US Embassy Tweeted to Clear Beijing’s Air’

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Indoor Air Quality

Man with Gas Mask

Air quality is a significant concern for homes and businesses alike. The technological and material demands of modern life mean that more and more pollutants are being released into the atmosphere. Unknowingly we breathe in a host of noxious particulates and trace gases, many of which can adversely affect our health. Though shielded from vehicular and industrial emissions, indoor air fares no better in the air quality stakes. Much of what we breathe is recycled from the outside and then combined with indoor contaminants such as dust, mould, asbestos and vapour from cosmetics and cleaning products. Poor ventilation and faulty heating systems cause a build-up of undiluted air, thereby increasing the chance of exposure to harmful pollutants.

Air quality hazards

Although some are at greater risk than others (those who work in the manufacturing, construction or cleaning industries to name a few), no one is completely safe from the hazards of indoor air. Seemingly unaccountable instances of ill health (headaches, dizziness, nausea, poor concentration, allergic reactions etc.) are not uncommon in the workplace and may in fact be related to indoor air quality. Tobacco smoke, perfume and other VOCs from new furnishings and electrics combine with ozone to produce unpleasant smells, skin irritation and even breathing difficulties. Although symptoms vary from person to person, both in type and severity, they are grouped together under the term Sick Building Syndrome (SBS). SBS is a wide-ranging yet poorly understood phenomenon with major implications not only for individual health but also productivity and wellbeing in the workplace. Characterized by a series of subjective health complaints, and therefore undiagnosable in strict medical terms, SBS has, by some, been seen as a product of (post)modern health-and-safety hysteria (‘a diversity of ill health effects, mostly minor and associated with a building, for which [there is] no specific cause’). And yet it is precisely this lack of specificity that makes it such an interesting, research-worthy phenomenon. Michelle Murphy, author of Sick Building Syndrome and the Problem of Uncertainty, conjectures that certain ‘power regimes’ (here she cites chemical corporations, tobacco companies, manufacturers and even some government organisations) are in fact capable of manipulating air sampling data in such a way that befits their anti-regulation agenda. Whether this is true or just another conspiracy theory exceeds the scope of this post, but it certainly makes for interesting debate!

SBS management strategy

Whilst the problem of uncertainty grows, it seems wholly appropriate that some sort of SBS management strategy be implemented, particularly in areas where issues of productivity are at stake. Of course, the fact that no two buildings are exactly alike makes this exceedingly difficult, as there can be no ‘one-size-fits-all’ solution. It is therefore imperative that high-risk indoor spaces be individually assessed to investigate further the causes of SBS. Air sampling seems like a sensible place to start.

Indoor Air Quality