(1) Habitable rooms must be provided with exterior windows or doors having a total glazed area of at least ten percent of the floor area, or they must have artificial light.

(2) An area equal to a minimum of five percent of the floor area must be available for unobstructed ventilation. Glazed areas do not need to be opened if a mechanical ventilation system is provided. The mechanical ventilation system must be capable of producing a change of air in the room every thirty minutes with at least one-fifth of the air supply taken from outside the commercial coach.

(3) Each bathroom must be provided with artificial light and with external windows or a mechanical exhaust must be provided. The external window must have at least 1/2 square feet of glazed area fully able to open. A mechanical ventilation system must be capable of producing a change of air every twelve minutes. Any mechanical ventilation system must exhaust directly to the outside of the commercial coach.