The body shall be constructed of fire-resistant material and the materials used inside the passenger compartment. The body shall be reasonably dustproof, gasproof, weathertight, and fume proof, and openings between the chassis and passenger compartment, where applicable, shall be sealed to prevent fumes or gases from entering the vehicle body. The body manufacturer shall indicate in a permanent and readily visible location on the body the month and year of final completion of the vehicle. The floor in the passenger compartment shall be level, except in the wheel housing, toeboard, stepwell, fuel fill pipe, and driver's platform areas which shall be constructed of fire resistant material. Rub Rails. One rub rail shall: Be located approximately at the floor line; Cover the same longitudinal area as the upper rub rail, except at wheel housings; and Extend to the radii of the right and left rear corners of the vehicle. One rub rail shall: Be located on each side of the bus approximately at seat level; and Extend from the rear side of the entrance door completely around the bus body, except for the emergency door, to a point of curvature near the outside cowl on the left side. Both rub rails shall be: At least 4 inches in width; Of 16-gauge steel; Corrugated or ribbed; Attached at each body post and all other upright structural members; and Applied outside the body or outside the body posts, pressed in or snap on rub rails not satisfying this requirement. A snow rail, if required, shall be installed the full length of the body skirt. Snow and floor line rails shall be screwed or huck bolted on and may not be an integral part of the body. The inside body height shall be 65 inches or more, measured metal to metal, at any point on the longitudinal center line from the front vertical bow to the rear vertical bow. The vehicle body shall be thermally insulated between the inner and outer panels, ceiling, roof, and walls with proper material to deaden sound and to reduce vibrations to a minimum. Projections and Exposed Edges. The interior of the vehicle, including the ceiling, shall be free of projections except those required for the installation of equipment approved by the Administration. An inner liner shall be provided on the ceiling and walls. Rearward components shall be lapped over forward components to reduce the likelihood of injury from exposed edges. Exposed edges shall be beaded, hemmed, or flanged. Storage Compartment. A fire resistant container of adequate strength and capacity for the storage of tire chains, or tow chains and tools for minor emergency repairs, may be provided. If inside, the compartment shall have a cover and be fastened to the floor of the vehicle. A seat cushion may serve as a storage compartment cover. Ventilation. The body shall be equipped with a suitable controlled ventilating system of sufficient capacity to maintain a proper quantity of air under normal operating conditions, without opening windows except in extremely warm weather. A static type exhaust roof ventilator is required, which: Shall be nonclosable; and May be incorporated into the roof vent or emergency exit.