Flame King's 10,000 BTU and 20,000 BTU radiant heaters are rated for indoor use in well-ventilated spaces, which means a room with at least one door or window open. They feature thermostatic temperature control, auto-ignition, a safety fuel shutoff, a safety tilt shutoff, and an exterior grate guard. The catalytic outdoor heater and 60,000 BTU forced-air blower are for outdoor use only. Regardless of the heater type, Flame King strongly recommends installing a CO detector whenever operating any propane appliance in a partially enclosed setting.

A 20 lb propane tank holds approximately 430,000 BTUs of energy. At full output, the Flame King 60,000 BTU forced-air blower heater runs for about 7 to 8 hours per tank. The 20,000 BTU radiant heater would run for roughly 20 or more hours per tank at full output. The 10,000 BTU model would run for approximately 40 hours. On their thermostat settings, actual runtime will be longer as the heater cycles on and off to maintain the set temperature.