"Air pollution both inside and outside the home causes at least 40,000 deaths a year in the UK, according to new report, which estimates the cost of the damage at £20bn." This quote came from a Guardian article last year, commenting on a report released by the Royal College of Physicians and the Royal College of Paediatrics and Child Health.

The article continues, "Outdoor pollution, much of it from vehicles, causes 40,000 deaths a year in the UK but the number linked to indoor pollution is not known. However, indoor air pollution is estimated to have caused or contributed to 99,000 deaths across Europe in 2012, the report states."

The primary focus for the report was domestic premises based, but indoor air quality (IAQ) can also be an issue in our offices, shops and schools. Below you can see five factors you may want to consider in establishing the best IAQ for your premises. 

1. What does the term "IAQ" cover?

Indoor air quality relates in its broadest sense to the quality of air within buildings and the potential effects (or not) it may have for the comfort and health of any occupants.

The quality of indoor air can be characterised and affected by the levels of dusts/particles, gases, chemical and microbiological material within it. The types of material comprising your indoor air can vary significantly over time depending on the type of premises you have, how it is ventilated, managed and maintained, as well as what it contains and processes/activities occurring.

The effect poor indoor air quality can have again will vary significantly depending on the types and levels of "pollutants" or "contaminants". These can trigger very specific reactions in individuals (i.e. allergic type reactions to a particular allergen) or affect groups of people indiscriminately (raised carbon dioxide levels, for example).

2. Where do these "contaminants/pollutants" come from?

As well as the primary gases that make it up - nitrogen, oxygen, carbon dioxide, other gases (e.g. argon) and varying levels of water vapour - our air also contains various material from the environment around it.

Particles of dust and debris are naturally picked up in air streams and will be affected by the type of environment (rural/urban) as well as more localised factors such as industry, traffic and construction. Gaseous pollutants are affected by the local environment in the same way. Biological pollutants in air can vary significantly and depend on atmospheric conditions as well as seasonal variation. Fungal spores, pollen and leaf litter for example are very seasonal, while bacteria tend to like to travel on vectors (other particles) and so wind conditions and humidity can have an effect.

Specific chemical pollutants such as Radon are primarily dictated by location and to a lesser extent, building materials. Our buildings and their internal environment can also have an effect on indoor air quality.

As well as vehicle emissions, construction/demolition work, local industry and agriculture can all contribute to the contamination found in outside air. The time of year and weather conditions will also influence the levels and types of contaminants.

3. How does my building affect IAQ?

For outside air pollutants, whether your building is naturally or mechanically ventilated - and the extent to which it is mechanically ventilated - has the most direct effect.

  • Naturally ventilated buildings have little control over what entrains into the building.
  • Mechanically ventilated (forced air/ air conditioned) buildings, depending on system configuration, and through the levels of filtration they contain, will remove varying percentages of the particulate and biological debris in outside air, and may temper and possibly humidify/dehumidify it.

IAQ in naturally ventilated buildings will vary dependent on conditions such as the number of open and closed windows and prevailing winds.

For mechanically ventilated buildings, how the system is configured, the quality and fitment of the installed filtration and the ductwork distribution system will all have affect. In addition to this, any installed terminal boxes, the extent of air recirculation and of course the standards of prevailing maintenance will also affect IAQ.

Building design and operation also have a direct effect on indoor air quality. From a design perspective, re-modelling or change of use can lead to system imbalances and therefore poor or inadequate ventilation to parts or all of the building. The poor siting of ventilation system air intakes can increase the levels of contaminants being drawn into the building - and not just particles and bacteria, those annoying cooking smells can come from this too! 

How the space is occupied, laid out and what happens within it has an effect too. For example:

  • Over population (numbers of people -v- capacity of supply/extract ventilation rates) can affect dust and carbon dioxide levels.
  • Volatile organic compounds (VOC) and other chemicals can be released from furnishings, cleaning products and various building products (glues, mastics, paints, etc.).
  • Printers, copiers and other equipment can add to the dust/particulate load in the immediate area.
  • High humidity levels in particular can cause issues with fungi/moulds.
  • Energy saving measures such as increased air recirculation or reduced run time for mechanically ventilated systems will also have an impact on IAQ.​

4. Why should I be considering IAQ?

Indoor air quality plays a significant role in the well-being, health and comfort of building occupants and it is an aspect of the building we feel rather than see. It is, with temperature, one of the most complained about aspects of the workplace too whether justifiably so or not.

External air quality has become a regular and increasingly measured topic. Poor indoor air quality is also gaining more focus and it has historically been linked with direct problems such as Sick Building Syndrome. It has also been linked to productivity (good IAQ improves it and poorer IAQ reduces it) and more recently impaired learning in schools for example.

The Workplace (Health, Safety and Welfare) Regulations 1992, cover a number of areas of the workplace environment including, lighting (Regulation 8), cleanliness (Regulation 9), temperature (Regulation 7) and ventilation (Regulation 6) where it states "6.-(1) Effective and suitable provision shall be made to ensure that every enclosed workplace is ventilated by a sufficient quantity of fresh or purified air."

L24 the Approved Code of Practice associated with the Regulations highlights:

  • "28 Enclosed workplaces should be sufficiently well ventilated so that stale air, and air which is hot or humid because of the processes or equipment in the workplace, is replaced at a reasonable rate.
  • 29 The air which is introduced should, as far as possible, be free of any impurity which is likely to be offensive or cause ill health.
  • 30 In many cases, windows or other openings will provide sufficient ventilation in some or all parts of the workplace. Where necessary, mechanical ventilation systems should be provided for parts or all of the workplace, as appropriate.
  • 31 Workers should not be subject to uncomfortable draughts. In the case of mechanical ventilation systems it may be necessary to control the direction or velocity of air flow. Workstations should be re-sited or screened if necessary.
  • 32 In the case of mechanical ventilation systems which recirculate air, including airconditioning systems, recirculated air should be adequately filtered to remove impurities. To avoid air becoming unhealthy, purified air should have some fresh air added to it before being recirculated. Systems should therefore be designed with fresh air inlets which should be kept open.
  • 33 Mechanical ventilation systems (including air-conditioning systems) should be regularly and properly cleaned, tested and maintained to ensure that they are kept clean and free from anything which may contaminate the air."

The Control of Substances Hazardous to Health Regulations 2002 and guidance in Health and Safety Executive document EH40/2005 Workplace Exposure Limits as well as other industry guidance, for example CIBSE Guide A, Environmental Design (A8 Health Issues) provides further information.

Knowing what your IAQ profile is and how your premises are supporting your indoor environment management is not just good from a legal perspective but from a health, wellbeing and productivity perspective too.

5. What can I do to assess my IAQ?

Having been assessing indoor air quality for over 30 years, the team at Assurity Consulting has an excellent understanding of the measurement and management and the issues that can surround IAQ. Your assessment should not only measure your IAQ in terms of microbiology, particles/dusts and relevant gases, but consider other variables such as:

  • temperature;
  • relative humidity;
  • airflow velocity;
  • noise and;
  • light levels.

You also need to assess how the building is ventilated, the supply and extract distribution system, external factors affecting outside air, the layout of the floors, the activities being carried out and their occupation.

Many building managers have, for years, monitored temperature and humidity in the occupied spaces of their buildings. Technology is now opening up our ability to also routinely monitor gases and wearable tech. While they do have their place and provide information, there is no substitute for an independent, trained assessor with accurately calibrated equipment and a clear understanding of your building's systems and other potential influencing factors looking beyond the obvious.

Important considerations with IAQ and potential influencing factors could include:

  1. IAQ issues/complaints may be the result of a single factor or a combination of factors.
  2. The type, nature and number of complaints, if any, and the length of time over which they have occurred.
  3. What presents as an issue "I'm too hot" may not be caused by just the space temperature. Airflow and/or carbon dioxide levels to name but two other factors could be the cause.
  4. The air handling unit is not always the culprit for which cleaning will remedy the situation, but it does need to be included in any assessment where relevant. Mode of air delivery and terminal boxes are also factors.
  5. Any recent changes, use of area/refurbishment/levels of occupation, etc.
  6. The local external environment and any changes that may have occurred.
  7. Fresh air make up, ventilation rates and system balance - any changes to plant run times, volumes or recirculation rates.


For the most part we find the indoor air quality in our customers' buildings confirms conditions are conducive to a healthy and productive environment. It is the result though of many things done well and regular independent checks. 

Assurity Consulting are leading experts in workplace health, safety and environmental compliance. For over 30 years we have worked with organisations of all sizes, working with them to measure, track and improve indoor air quality in their buildings. For more information on our services, please contact us on tel. +44 (0)1403 269375 or email us

DOWNLOAD PDF