class B
Classification for a fire assembly having a 1-hour or 1 1/2 hour fire-resistance rating for protecting openings in 1-hour or 2-hour fire separations, exit stairways, and vertical shafts. (Ching, 1995)
Classification for a fire assembly having a 1-hour or 1 1/2 hour fire-resistance rating for protecting openings in 1-hour or 2-hour fire separations, exit stairways, and vertical shafts. (Ching, 1995)