Intent 1:
[Clauses 9.32.3.4.(8)(a) and 9.32.3.4.(8)(b)] To limit the probability of the
premature failure of outdoor air supply fans, which could lead to
the inadequate replacement of indoor air with outdoor air.
This is to limit the probability of the inadequate control
of:
- airborne pollutants,
- oxygen and other components necessary for breathable
air, or
- relative humidity, which could lead to condensation,
which could lead to the generation of pollutants from biological growth
or from materials that become unstable on wetting.
This is to limit the probability of negative effects on
the air quality of indoor spaces, which could lead to harm to persons.
Intent 2:
[Clause 9.32.3.4.(8)(c)] To limit the probability
that the outdoor air supply flow will not be equal to the normal operating
exhaust capacity of the principal ventilation fan, which could lead
to:
- excessive negative pressure, or
- excessive positive pressure.
This is to limit the probability of:
- the inadequate control of airborne pollutants, or oxygen
and other components necessary for breathable air,
- the inadequate control of relative humidity, which could
lead to condensation on interior surfaces,
- where there is excessive negative pressure:
- the ingress of soil gases (such as methane and radon),
- the spillage of combustion products from fuel-burning
appliances that are susceptible to spillage, or
- moisture ingress from the ground, or
- where there is excessive positive pressure, condensation
within assemblies.
This is to limit the probability of negative effects on
the air quality of indoor spaces, which could lead to harm to persons.