In depressurization situations where air exhausting devices operate without adequate replacement of indoor air with outdoor air, to limit the probability of 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.
[Clause 9.32.3.6.(1)(b)] To expand the application of Articles 9.33.6.12. and 9.33.6.13. to exhaust-only ventilation systems.