A gas furnace is to be installed in a garage. The burners and ignition sources must be located ______ above the floor.

For safety reasons, gas furnace burners and ignition sources must be installed at least 18 inches above the garage floor. This height is critical because garages can accumulate flammable vapors from vehicles, gasoline, and other materials. By positioning the burners and ignition sources above this height, the risk of ignition from these vapors is significantly reduced.

When installed at or above 18 inches, the furnace minimizes the chances that it will come into contact with these potentially hazardous vapors, thereby enhancing safety and compliance with building codes. This standard is designed to protect both the equipment and the environment within the garage, ensuring that any flammable gas or fumes remain at a safe distance from ignition sources. Thus, the requirement for the placement of the burner and ignition sources is properly addressed by specifying an installation height of at least 18 inches from the garage floor.