Intent 1:
To limit the probability of an inability to regulate
the flow of outdoor air in ventilation systems, which could lead to:
- an outdoor air supply flow that is less than the normal
operating exhaust capacity of the principal ventilation fan, which
could lead to inadequate ventilation or excessive negative pressure,
or
- an outdoor air supply flow that is greater than the
normal operating exhaust capacity of the principal ventilation fan,
which could lead to excessive positive pressure.
This is to limit the probability of:
- 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.