The Ontario Building Code | Exterior Exit Passageways

9.10.17.4. exterior Exit Passageways

(1) Where an exterior exit passageway provides the only means of egress from the rooms or suitesit serves, the wall and ceiling finishes of that passageway, including the soffit beneath and the guard on the passageway, shall have a surface flame-spread rating of not more than 25, except that up to 10% of the total wall area and 10% of the total ceiling area is permitted to have a surface flame-spread rating of not more than 150.