The Ontario Building Code | Twenty-Minute Closures
18.104.22.168. Twenty-Minute Closures
(1) A door assembly having a fire-protection ratingnot less than 20 min is permitted to be used as a closurein,
(a) a fire separation not required to have a fire-resistance rating more than 1 h, located between,
(i) a public corridor and a suite,
(ii) a corridor and adjacent sleeping rooms, or
(iii) a corridor and adjacent classrooms, offices and libraries in Group A, Division 2 major occupancies, or
(b) a fire separation not required to have a fire-resistance rating more than 45 min, located in a buildingnot more than 3 storeys in building height.
(2) The requirements for noncombustiblesills and combustible floor coverings in NFPA 80, "Fire Doors and Other Opening Protectives", do not apply to a door described in Sentence (1).
(3) A door described in Sentence (1) shall have a clearance not more than 6 mm at the bottom and not more than 3 mm at the sides and top.
(4) In elementary and secondary schools, a door assembly conforming to Articles 22.214.171.124. and 126.96.36.199. is permitted to be used as a closure in a fire separationhaving a fire-resistance rating of 30 min.