Ducts shall not serve both upper and lower combustionĪir openings where both such openings are used.

Ducts shall terminate in an unobstructed space, allowingįree movement of combustion air to the appliances.

Having equivalent corrosion resistance, strength, andĮxception: Within dwellings units, unobstructed studĪnd joist spaces shall not be prohibited from conveyingĬombustion air, provided that not more than one fireblock

Ducts shall be constructed of galvanized steel or a material.

FIGURE 701.6.1(2) COMBUSTION AIR FROM OUTDOORS THROUGH VENTILATED ATTIC FIGURE 701.6.1(3) COMBUSTION AIR FROM OUTDOORS THROUGH HORIZONTAL DUCTS Ĭomply with the following : INLET AIR FROM VENTILATED CRAWL SPACE AND OUTLET įIGURE 701.6.1(1) COMBUSTION AIR FROM OUTDOORS M 2/kW) of total input rating of appliances in theĮnclosure. Of not less than 1 square inch per 2000 Btu/h (0.001 Horizontal ducts, each opening shall have a free area

Where communicating with the outdoors through.Total input rating of appliances in the enclosure. Than 1 square inch per 4000 Btu/h (0.0005 m 2/kW) of Where communicating to the outdoors through verticalĭucts, each opening shall have a free area of not less Where directly communicating with the outdoors or.The openings shall communicateĭirectly, or by ducts, with the outdoors or spaces thatįreely communicate with the outdoors as follows: Within 12 inches (305 mm) of the bottom of the enclosure, (305 mm) of the top of the enclosure and one commencing

Permanent openings, one commencing within 12 inches

1 2 4 combustion air