Heated surfaces having a temperature sufficient to ignite vapors shall not be located in flammable vapor areas. Space-heating appliances, steam pipes or hot surfaces in a flammable vapor area shall be located such that they are not subject to accumulation of deposits of combustible residues.
Exception: Drying apparatus complying with Section 2404.6.1.2.
- 28 gauge sheet metal on 1/4 inch (305 mm) insulating millboard 12 inches
- 28 gauge sheet metal on 1/8 inch insulating millboard spaced out 1 inch (254 mm) on noncombustible spacers 9 inches (230 mm).
- 22 gauge sheet metal on 1 inch rockwool bats reinforced with wire mesh or the equivalent 3 inches (76 mm).
- Any other approved material of equal or greater fire-resistance.