To limit the probability that air-exhausting devices required by Sentence 9.32.3.8.(2) will operate without adequate replacement with outdoor air, which could lead to excessive negative pressure in dwelling units, which could lead to the spillage of carbon monoxide gas from fuel-burning appliances that are susceptible to spillage, which could lead to the acute poisoning or asphyxiation of persons.
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.