Indoor Air Quality

Indoor Air Quality

Indoor air quality (IAQ) is a term which refers to the air quality within and relates to the health and comfort of building occupants. Indoor air quality (IAQ) is strongly influenced by the emission of Volatile Organic Compounds (VOCs) including odorants which have a direct influence on people’s well-being and health. Uncommon or intense odours may have a negative psychological influence on occupants. The suppression of VOCs may be achieved by ventilation, the specification of low emission materials or the use of materials with air purification properties, all of which improve air quality indoors.


Indoor air pollutants include very-VOCs (such as formaldehyde), VOCs (such as benzene, aldehydes and ketones, fragrance compounds), semi-VOCs (such as PAHs, flame retardants), inorganic pollutants (such as particles and fibres), allergens, radioactive gases such as radon, and pollutants of microbiological origin such as moulds or fungi (including spores and endotoxins). Pollutants can originate from outdoor sources, such as traffic and other forms of combustion (CO, NOx, SOx), or from indoor sources, such as people, their activities, tobacco smoke, building and furnishing materials, electronic equipment, cleaning products or heating, ventilation and air-conditioning (HVAC) systems.


There is growing literature on the effects of exposure to the various compounds with the World Health Organization (WHO, 2010) commenting that while combined exposure is inevitable, there is limited data on the quantified effects. However, for ease of analytical measurements and comparing levels the amounts of VOCs are summed and expressed as Total Volatile Organic Compounds (TVOC). Mølhave et al., (1997) provided an approximate guideline on the potential impacts on health associated with levels of TVOC as given in Table 1.


Table 1: Impact of TVOC (Mølhave et al., 1997)

Values of TVOC Health impact
< 200 µg/m3 No irritation or discomfort expected
200 – 3,000 µg/m3 Irritation and discomfort may be possible
3,000 – 25,000 µg/m3 Discomfort expected and headache possible
> 25,000 µg/m3 Toxic range where other neurotoxic effects may occur


The associated symptoms of the building related illness that can be caused by the deterioration of IAQ can include:

  • headaches;
  • eye, nose or throat irritations;
  • dry coughs;
  • allergy reactions;
  • dry and itching skin;
  • nonspecific hypersensitivity;
  • insomnia;
  • dizziness and nausea;
  • difficulty in concentrating and tiredness.

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About Helen Cornwell

Helen Cornwell is the Project Manager for the EU funded project ISOBIO (Development and Demonstration of Highly Insulating, Construction Materials from Bio-derived Aggregates) and Networking Coordinator for the ECO-SEE project (ECO-innovative, Safe and Energy Efficient wall panels and materials for a healthier indoor environment).


  1. Helen Cornwell says

    A very interesting article. For further details on this problem, interested readers may also wish to read: Crump D., Dengel A. and Swainson M., IAQ in highly energy efficient homes – a review (2009) NHBC Foundation report NF18, IHS BRE Press, Watford. ISBN 1 84806 1040; Yu, C. and Kim, J T (2011). Low-carbon housing and indoor air quality. Indoor and Built Environment. 21 (1), 5-15.

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