Natural or mechanical ventilation for the removal of products of combustion shall be provided on every story and shall consist of one of the following methods:
A. Easily identifiable windows or panels which are manually openable shall be provided in the exterior walls. When openable windows or panels are used, all windows/panels in the building above the first floor shall be openable.
B. The interior air circulation system may be used provided such system, under fire conditions, exhausts at a minimum of six complete air changes per hour. Such systems shall be exhausted directly to the outside of the building. System shall be so designed that the maximum required change can be achieved in two separate smoke removal zones at the same time during normal and emergency standby power conditions. (Prior code §§ 9.28.1247, 15.13.1301)