The Ontario Building Code | Exterior Exit Passageway

3.1.13.10. exterior Exit Passageway

(1) The wall and ceiling finishes of an exterior exitpassageway that provides the only means of egressfrom the rooms or suites it serves, including the soffit beneath and the guard on the passageway, shall have a flame-spread rating not more than 25, except that a flame-spread rating not more than 150 is permitted for up to 10% of the total wall area and for up to 10% of the total ceiling area.