Heaters shall be of a hot water type. The heating system shall be capable of maintaining a temperature of not less than 50°F throughout the vehicle at the average minimum January temperature established by the National Weather Service, National Oceanic and Atmospheric Administration, for the area in which the vehicle is to be operated. Heaters shall bear a name plate attached by the manufacturer which shall indicate the heater rating and which shall constitute certification that the heater performance is as shown on the plate. Heater hoses shall be adequately supported to guard against excessive wear due to vibration, and may not dangle or rub against the chassis or sharp edges and may not interfere with or restrict the operation of any engine function. Heater lines inside the passenger compartment shall be shielded to prevent accidental contact or scalding of the driver or passengers. Dual Heater Installation. Each dual heater installation, if so equipped, shall: Include a shut-off valve on each heater hose located in the engine compartment or under the body to the rear of the right front wheel on each heater hose; Be secured to the underside of the chassis to prevent abrasion or damage; and Be of a type to withstand weathering and abrasion of this exposed location. One heater shall be located at the front of the vehicle as original equipment. If an auxiliary heater is used, it shall be located as far to the rear of the passenger compartment as possible. Combustion Heaters. Combustion heaters are permitted and shall: Have a switch or one-way valve installed at the fuel tank when the fuel line is pressurized to shut off the fuel to the heater in case of a broken line; Have an indicator light in the driver's compartment to alert the driver of a malfunction; Be mounted on the left side of the vehicle in an individual compartment opening from the outside; and Have the exhaust come out the left side of the vehicle under the skirt as close to the rear wheels as possible. Only combustion heaters approved by the Administration may be installed on school vehicles. Portable heaters may not be used.