Sentence 9.32.3.8.(4)

Intent 1:

To limit the probability that occupants will disable outdoor air supply fans, which could lead to excessive negative pressure.

This is to limit the probability of:

• 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, 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 9.32.3.8.(4)(b)] To limit the probability that outdoor makeup air will be perceived as a draft, which could lead to occupants disabling makeup air fans, which could lead to depressurization, which could lead to negative effects on indoor air quality, which could lead to harm to persons.

Intent 3:

To exempt mechanical air exhausting devices that are principal ventilation fans operating at a rate not greater than the maximum permitted in Table 9.32.3.3. from the provisions in Article 9.32.3.8. for outdoor makeup air fans, on the basis that Articles 9.32.3.4. and 9.32.3.5. address outdoor makeup air for the principal ventilation fan.