In addition to requirements of the Washington State Ventilation and Indoor Air Quality Code:

(1) The installation of each appliance must conform to the manufacturer's installation instructions. The manufacturer's instructions must be attached to the appliance.

(2) Combustion air inlets and flue gas outlets must be listed as components of the appliance and must be completely separated. The required separation may be obtained by:

(a) The installation of direct vent system (sealed combustion system) appliances; or

(b) The installation of appliances within enclosures so that the appliance combustion system and venting system are separate from the interior atmosphere of the commercial coach. There must not be any door, removable access panel, or other opening into the enclosure from inside the commercial coach. Any openings for ducts, piping, wiring, etc., must be sealed.