Section 279 - Fire alarm signal systems and fire drills1. Fire alarm signal systems. Except as may otherwise be provided by the board in its rules, every factory building over two stories in height in which more than twenty-five persons are employed above the ground floor shall be equipped by the owner thereof with a fire alarm signal system having a sufficient number of signals clearly audible to all occupants of the building, and so arranged as to permit the sounding of all the alarms within the building whenever the alarm is sounded in any portion thereof. Such system shall be maintained in good working order and no person shall tamper with same or render ineffective any portion thereof except to repair it. A person discovering a fire shall cause an alarm to be sounded immediately. The board of standards and appeals in the city of New York and elsewhere the board may make rules and regulations relating to the installation of fire alarm signals and prescribing the number, character and location of the signals and the method and character of the installation including that of all appliances in connection therewith.2. Fire drills. Except as may otherwise be provided by the board in its rules, in every factory building over two stories in height in which more than twenty-five persons are employed above the ground floor, a fire drill shall be conducted at least once a month in which all of the occupants of the building shall participate simultaneously and which shall conduct all such occupants to a place of safety. In New York city the fire commissioner and elsewhere the board shall make rules, regulations and special orders necessary or suitable to each situation and to secure the personal co-operation of all the tenants of the building in a fire drill of all the occupants thereof. Such rules, regulations and orders may require the posting of the same or an abstract thereof and may prescribe upon whom shall rest the duty of carrying them out.3. Exceptions. Subdivisions one and two of this section shall not apply to a building in which every square foot of the floor area on all stories is protected with an automatic sprinkler system having two adequate sources of water supply and approved by the public authorities having jurisdiction thereof and in which also the maximum number of occupants of any one floor does not exceed by more than fifty per centum the capacity of the exits, as determined by subdivisions one, two, three and four of section two hundred and seventy-eight. If the commissioner after investigation determines that the spirit of this chapter is observed and public safety secured he may permit in place of the automatic sprinkler system before specified an automatic sprinkler system having one adequate source of water supply and approved by the public authorities having jurisdiction thereof.4. The provisions of this section shall be enforced in the city of New York by the fire commissioner of said city and elsewhere by the commissioner.