The minimum free area of each of the two combustion air openings required for a gas furnace with an input rating of 92,000 Btuh communicating with the outdoors through horizontal ducts is ____ square inches.
The minimum free area of each of the two combustion air openings required for a gas furnace with an input rating of 92,000 Btuh communicating with the outdoors through horizontal ducts is ____ square inches.