Indoor Air Quality
2. What are the main factors in indoor air quality?
Pets and pests are sources of allergens
The main factors that determine indoor air quality are:
- Chemicals: Two common causes of
complaint regarding poor indoor air quality are bad smells
and irritation of the eyes, nose and throat. Such irritation
may be induced by specific chemicals, but also by factors
such as dry air. Bad smells are not harmful in themselves
but may cause unpleasant effects and increase symptoms such
as headache, nausea, and irritation of eyes or throat. The
hazards associated with chemicals and their effects on
health are not always well known, particularly for long term
Radon is a gas that occurs naturally in soil and rock in
some regions and that can get inside buildings by diffusing
through the soil. In indoor air, it can lead to lung
- Suspended particles: Coarse,
fine and ultrafine
particles in ambient air are known to cause adverse health
effects, including on the respiratory and
Particles may in part come from outdoor pollution, but can
also form indoors by the burning of fuels for heating and
cooking, and by reactions between
ozone and some
volatile organic compounds
(VOCs). In addition, man-made
nanoparticles, that are
increasingly used in consumer products, may have an impact
as indoor air pollutants.
- Microbes: Microorganisms such as
viruses may play a role
in the development of
allergies involving the
airways. This is for instance a problem in damp buildings or
indoor environments where there is
mould because many
fungi release substances that cause allergies.
Virus infections may
also be transmitted by indoor air and some of them can lead
to an increase in asthma and allergies.
- Pets and pests: Indoors, pests, house
dust mites, cockroaches, and – in inner cities in particular
– mice are important sources of
allergens can lead to diseases of the airways,
rhinitis, and asthma.
Exposure varies depending on the type of environment and
cultural habits. How much contact with pets affects the
development of asthma in people remains unclear. However,
allergic people should
avoid exposure to substances to which they are allergic.
- Humidity: There is an optimal level
of humidity in indoor air. Too low humidity causes eye
irritation, dry skin, and rashes, whereas too high humidity
results in water damage and mould problems and favours the
growth of dust mites.
- Ventilation: It is one of the most
important factors determining indoor air quality. Poorly
aired offices and schools, for instance can affect health
and work or academic performance. Controlled ventilation is
especially needed in heavily insulated buildings that allow
little air exchange with the outside.
- Temperature: As well as causing
discomfort, indoor air that is very cold or hot is highly
unhealthy. Air that is too warm, for example, aggravates the
effects of insufficient humidity.