Ala. Code § 9-17-122
The following LP-gas room heaters may be installed in a used manufactured home as follows:
LP-gas listed vented room heaters equipped with a 100 percent safety pilot and a vent spill switch or LP-gas listed unvented room heaters equipped with factory equipped oxygen depletion safety shut-off systems may be installed in a used stationary manufactured home (mobile home) but not in sleeping quarters or bathrooms in the manufactured home (mobile home) when the installation of the heater is not prohibited by the appliance manufacturer and when the input rating of the room heater does not exceed 20 BTU per hour per cubic foot of space and combustion and ventilation air is provided as specified in the National Fuel Gas Code, NFPA 54, as adopted by the board. All room heaters installed pursuant to this section shall be securely anchored to the wall or floor.
Ala. Code § 9-17-122 (1975)