Division .7 F1

Doors and door frames in ‘B’ class divisions and means of securing them shall provide a method of closure which shall have resistance to fire equivalent to that of the divisions except that ventilation openings may be permitted in the lower portion of such doors. Where such opening is in or under a door the total net area of any such opening or openings shall not exceed 0,05 m ² . Alternatively, a non-combustible air balance duct routed between the cabin and the corridor and located below the sanitary unit is permitted where the cross-sectional area of the duct does not exceed 0,05 m ² . All ventilation openings shall be fitted with a grill made of non-combustible material. Doors shall be non combustible.