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Outdoor Air Quality
Good indoor air quality is essential for a healthy indoor environment,
yet increasing urbanisation and contaminant emissions into the atmosphere
is presenting difficulty. Significant sources of pollution include:
 Industrial pollution;
Pollution from
vehicles;
Pollution from adjacent
buildings;
Agricultural pollutants
(pollen, chemicals and sprays).
Preventive Measures
Preventive measures should be undertaken in the following order:
Controlling Emissions: Pollution should be controlled at
source. This is usually covered by legislation e.g.:
 US
Clean Air Act:
 European
Air Framework Directive
Siting of air intakes (and outlets): Many problems are caused
by siting air intakes close to sources of pollution. Guidance is published
by:
 Brian
Rock et al: 'The placement of ventilation air intakes for improved
Indoor Air Quality', ASHRAE Transactions, Chicago 1999. (United States);
 Irving
et al: CIBSE publication TM21 “Minimising pollution at
air intakes” CIBSE (UK);
 Netherlands:
'Regulations for the siting of air intakes and outlets', Air
Infiltration Review, June 1998.
Using the building to offer protection against outdoor pollution: A
building can offer protection by:
 Presenting
a physical barrier: A building can be effective at preventing
outdoor pollutants entering a space. The building must, however be very
airtight and occupants must rely on oxygen already in the space for
metabolism. This approach is only suitable to deal with short term rises
in outdoor pollutant (e.g. on a timescale of up to an hour [see Air
Quality Reservoir]).
Natural
'Decay' ozone and, possibly, other reactive pollutants: Certain
pollutants naturally 'decay'. Ozone, for example, is effectively converted into oxygen as it passes through
construction openings (masonry buildings are especially effective).
There is some evidence to suggest that soluble pollutants such as oxides
of nitrogen and sulphur also reduce in concentration as they enter
buildings. Respirable dust particles, however, (i.e. PM10's) enter
buildings without reduction.
Filtration:
Filtration is frequently used to remove dust particles. The removal of
gaseous pollutants and fine (respirable) dust particles, however,
requires expensive HEPA and gas adsorption filters. Despite the benefit
of filters, therefore, they should not be seen as an excuse to accept
poor outdoor air quality. Successful filtration solutions are expensive
and not suitable for the many buildings that are naturally ventilated or
excessively leaky. See also: Filtration.
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