Tractor Supply Company, The Home Depot and Amazon sell vent-free propane heaters. Unlike conventional gas heaters, these devices do not require venting to the outside, which makes installation easier. They are equipped with oxygen depletion sensors for safety.
Vent-free propane heaters are available in a variety of sizes and styles. Some use a catalytic system to produce infrared heat or the more traditional blue gas flame. However, state laws in California and Ohio make use of these systems in residential settings illegal.
Many vent-free heaters operate without electricity, allowing them to continue to provide heat in the event of a power failure. Some manufacturers offer an optional blower to provide more even heat distribution for larger areas. These heaters claim a 99 percent efficiency that reduces the production of exhaust gases, including potentially fatal carbon monoxide. The oxygen depletion sensor constantly monitors the oxygen level in the room and automatically shuts off the propane supply in the event of an emergency. For continued safe operation, units require regular service.
Some units produce as much as a gallon of water every 2.5 hours as a byproduct of combustion. The humidity level in a room with the heater is sometimes uncomfortable for occupants and causes moisture related issues.