Intent 1:
To limit the probability of:
- where both exhaust and supply ducts are undersized,
inadequate ventilation,
- where supply ducts alone are undersized, excessive negative
pressure, or
- where exhaust ducts alone are undersized, 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,
- condensation within assemblies,
- moisture ingress from the ground,
- the ingress of soil gases (such as methane and radon),
or
- the spillage of combustion products from fuel-burning
appliances that are susceptible to spillage.
This is to limit the probability of:
- the generation of pollutants from biological growth
or from materials that become unstable on wetting, or
- pollutant ingress (including combustion products and
soil gases).
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:
To expand the application of Subsection 9.33.4. to ducts in residential occupancies where
the size of a duct cannot be determined using Table 9.32.3.11.A. or 9.32.3.11.B.