To exempt separations between a dwelling unit and an attached garage from the fire-resistance rating requirements of Sentence 3.3.5.6.(1) on the basis that sufficient conditions are in place to minimize the threat to the occupants of the dwelling unit posed by fire and exposure to vehicle exhaust fumes, and the dwelling unit and the attached storage garage are sprinklered.
This [the separation and sprinkler protection] is to limit the probability that a fire involving the garage will spread to the dwelling unit, which could lead to harm to persons.
This [the door requirements, fume barrier and prohibition of air ducts] is to limit the probability that vapours will migrate from the garage into the dwelling unit, which could lead to their accumulation and subsequent ignition by a nearby ignition source, which could lead to a fire or explosion, which could lead to harm to persons.