M-1003.1 Air from the same room or space: The room or space containing fuel-burning appliances shall have a minimum volume of 50 cubic feet per 1,000 British thermal units per hour (Btuh) (4.83 m3/kW) of combined input rating of all appliances in the room. Combustion air requirements shall be determined based on the simultaneous operation of all fuel-burning appliances drawing combustion and dilution air from the room. In buildings of tight construction where the air exchange rate is less than 0.5 air changes per hour, additional air shall be provided in accordance with Section M-1004.0, M-1005.0 or M-1006.0.

M-1003.2 Air from adjacent spaces: Where the volume of the room in which the fuel-burning appliances are located does not comply with Section M-1003.1, additional inside combustion and dilution air shall be obtained by opening the room to adjacent spaces so that the combined volume of all communicating spaces meets the volumetric requirements of Section M-1003.1. Openings connecting the spaces shall comply with Sections M-1003.2.1 and M-1003.2.2.

M-1003.2.1 Number and location of openings: Two openings shall be provided, one within 1 foot (305 mm) of the ceiling of the room and one within 1 foot (305 mm) of the floor.

M-1003.2.2 Size of openings: The net free area of each opening, calculated in accordance with Section M-1008.0, shall be a minimum of 1 square inch per 1,000 Btuh (2201 mm2/kW) of input rating of the fuel-burning appliances drawing combustion and dilution air from the communicating spaces and shall be not less than 100 square inches (64516 mm2).