Stairway pressurization shall be installed as required by T-24 C.C.R., Chapter 33 and designed in accordance with N.F.P.A. Standard 92-A. Stairway pressurization shall also be designed that all exit doors into stairways, at all levels, shall be opened by exerting between eight pounds and thirty (30) pounds force in the direction of exit travel. Such systems shall not work against the smoke removal systems. Positive pressure shall be maintained with a minimum of three doors in the fully open position. (Prior code §§ 9.28.1253, 15.13.1307)