In a garage installation, at what height must the burner and ignition sources be located according to national standards?

The correct answer is that the burner and ignition sources must be located at a height of 18 inches according to national standards for garage installations. This specification is put in place primarily to minimize the risk of ignition from gasoline vapors, which can accumulate at lower levels in a garage environment. Gasoline vapors are heavier than air and can linger close to the ground, so placing the burner and ignition sources 18 inches above the floor helps ensure safety by reducing the likelihood that these sources will ignite any vapors that might be present. Following this standard is essential for preventing potentially dangerous situations and ensuring compliance with safety regulations.