Clearing the air: monitoring air quality in the workplace

Are there more pollution and health issues arising from traditional factory-type workplaces and their industrial processes, compared with ‘normal’ home or office working environments? Many employers would think so, but they are wrong. Although it is relatively easy to monitor exposure to noise, hazards and air pollution in factories, offices present more complex challenges. 

The US Environmental Protection Agency estimates that indoor pollution levels are often at least two times higher than ambient pollution levels in the outdoor environment, and occasionally up to 100 times higher. It is therefore vital that occupational health professionals, health and safety managers and occupational hygienists ensure regular monitoring of indoor air quality is undertaken, even in areas that may appear to be innocuous.

Are these pollutants being pulled into indoor environments from outside, or are they generated internally? Employees’ exposure to particles and solvents is not only affected by internal factors, but is also influenced directly by external ones. Even in air-conditioned buildings with efficient air intake filtration systems, some smaller ultra-fine particles and solvents can make their way inside.

Many studies have proven a direct link between indoor and outdoor air quality. The influence of atmospheric pollution on indoor air quality was studied in Santiago, Chile.1 Carbon monoxide (CO) was monitored indoors and outdoors in restaurants, offices and other places. The levels of CO changed simultaneously outdoors and indoors, especially during traffic rush hours, showing the importance of infiltrating outdoor air indoors.

Air quality is a subjective area, but many studies have shown that even very small amounts of pollutants can have a direct effect on employees’ comfort and productivity as well as on their respiratory health and wellbeing. In a separate study2 a pollution source (a 20-year-old used carpet) was concealed in an office. Five groups of six women were exposed to the office conditions twice; once with the pollution source present, and once with it absent. Each exposure was for 265 minutes in the afternoon, one group at a time.

The perceived air quality and Sick Building Syndrome symptoms were assessed while the subjects performed simulated office work. Twenty-two per cent were dissatisfied with the air quality in the office when the pollution source was present, and 15% were dissatisfied when the pollution source was absent. In the first group, there was a significantly increased prevalence of headaches and significantly lower levels of reported effort during the text typing and calculation tasks, both of which required a sustained level of concentration. Reducing the pollution load on indoor air proved to be an effective way of improving the comfort, health and productivity of building occupants.

Sick Building Syndrome symptoms

Symptoms associated with Sick Building Syndrome include headaches, eye, nose or throat irritation, dry mucous membranes, dry skin, nasal symptoms, breathing difficulties, abnormal taste sensation, distorted sense of smell, tiredness, dizziness, lack of concentration and nausea.

A diagnosis of SBS is supported by the presence of colleagues in the same environment experiencing such symptoms at the same times. Symptoms recognised by the World Health Organisation include:

  • Lethargy (57%)

  • Stuffy nose (47%)

  • Headache (43%)

  • Runny nose (31%)

  • Itchy eyes (28%)

  • Dry eyes (27%)

  • Flu-like symptoms (23%)

The common fundamental issue is that all the symptoms improve in people after they leave the building.

What are the major pollutants that affect indoor air quality?

Particles & PM10 (particulate matter 10 microns or less): Smoking is one of the biggest sources of particulates. Since anti-smoking laws have come into effect throughout the UK, the risks from inhalation of secondary tobacco smoke are declining in the workplace. Vehicles, especially diesels, generate high levels of particulates, which may enter the building if inlet filtration is not efficient. Dusts from other processes such as printing or shredding will be minimal in offices. Asthmatics are particularly susceptible to particulate pollution. Weather is also a contributory factor to indoor air quality as more pollution is formed on dry, windy days and more may be drawn in by the air conditioning systems.

Nitrogen oxide (NOx) and other toxic gases: Nitrogen oxide is readily emitted from vehicles and power stations and it converts into the more harmful nitrogen dioxide in the air. NOx can also be emitted from gas appliances such as cookers and hobs in domestic kitchens, often reaching considerable levels. This may trigger asthma attacks or cause breathing difficulties in those who are more susceptible.

Radon: This is responsible for half of every person’s radiation exposure. It is prevalent in areas with a high proportion of granite, such as Edinburgh, and although outdoor ambient levels of exposure are low, these are more concentrated indoors, especially if there is inadequate ventilation. Specialist detection badges and equipment or a monitoring service from the National Radiation Protection Board can be used.

Solvents: These are usually generated inside the building and come from a variety of sources including glue, furniture, carpets and fabrics. Even high usage of perfumes and deodorants, if no effective ventilation is in place, can build up to levels that can affect some people, especially those with low tolerance thresholds.

Carbon monoxide (CO): Many examples of buildings can be found where the air intakes have been fitted at street level, which can pull in and concentrate levels of pollutants such as CO, which has no odour and is very easy to overlook, often with serious consequences. The deaths last year of two children in a Corfu holiday resort, and two women in their home in Kent – in both cases from carbon monoxide poisoning – also highlight the risks of inadequately serviced boilers and badly ventilated buildings.

Moulds and fungi: Many people suffer respiratory problems when exposed to fungal spores. Breathing difficulties can be exacerbated by high levels of humidity and dampness. Both of these are affected by external air quality and atmospheric conditions. It is essential to ensure adequate levels of fresh air intake and efficient air filtration.

Thermal environment: Outdoor weather conditions often have even more impact on the indoor working environment. Even with air conditioning systems, employees may be exposed to high levels of solar heat gain via windows or be affected by radiant heat from the walls and fabric of the building. Humidity is a key element in air quality, and if the air is too dry, this may exacerbate conditions such as rhinitis and dry eyes. All these factors may lead to increased levels of stress, which in turn will affect employees’ wellbeing and productivity.

Monitoring the environment

A wide variety of instruments and equipment is available, which can be used to take readings and air samples from indoor environments. These include direct reading detection tubes or detectors for gases and vapours, particulate samplers or sampling pumps, heat stress meters, light meters, temperature and humidity detectors and dataloggers.

Data on the ambient air quality is also available from local authorities. Such information can be used to ascertain what effect ambient air quality may be having on the occupants of a building. For a more detailed example, visit

World Health Organisation guideline levels for typical indoor pollutants

CO < 5ppm
CO2 < 1500ppm
Formaldehyde < 0.1ppm
NO2 < 0.15ppm
Ozone < 0.08ppm
Respirable dust < 0.15ppm
Bacteria < 1500cfu/m3
Fungi/yeasts < 750cfu/m3

(ppm – parts per million denotes one particle of a given substance for every 999,999 other particles)
(cfu/m3 – denotes colony-forming units per cubic metre of air) 

Gary Noakes is product manager at environmental monitoring firm Casella Measurement

    1.  Indoor and Built Environment, Vol. 6, No. 6, 320-330 (1997)
    2.  Pawel Wargocki, David P Wyon, Yong K Baik, Geo Clausen, P Ole Fanger (1999) 
    3.  Perceived Air Quality, Sick Building Syndrome Symptoms and Productivity in an Office with Two Different Pollution Loads
    4.  Indoor Air 9 (3), 165–179

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