Sentence 9.32.3.8.(7)

Intent 1:

To limit the probability of excessive negative pressure, which could lead to:

• 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.

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 exempt certain dwelling units from the requirement to provide makeup air [see Sentences 9.32.3.8.(1) to 9.32.3.8.(5)], where it can be shown using test procedures described in CAN/CGSB-51.71 that maximum depressurization levels will not likely cause the spillage of combustion products from fuel-fired appliances.