Quick answer
A propane heater is safe indoors only if its rating plate says it is certified for indoor use, it has an oxygen-depletion sensor and a tip-over shut-off, and you run it with a window cracked and a working carbon monoxide alarm. Construction torpedo heaters, tank-top radiant heaters, barbecues and patio heaters must never be used inside. Barbecue-size cylinders stay outdoors under the propane code.
Whether it is safe to use a propane heater indoors when the furnace is out depends on which heater, and the answer is printed on it. A small number of portable propane heaters are certified for indoor use. Most of what people have in the garage is not, and the difference is not a technicality: an outdoor heater has no way to notice that the room is running out of oxygen.
What makes a propane heater indoor-rated
- A certification label that names indoor use. Look for the CSA or equivalent mark on the rating plate and read the line beside it. If it says outdoor use only, or construction use, that settles it.
- An oxygen-depletion sensor. It is a pilot assembly that shuts the gas off when the oxygen in the room drops, before incomplete combustion starts producing carbon monoxide in quantity.
- A tip-over shut-off that closes the gas valve when the heater is knocked or tilted.
- A stated room size and a stated ventilation opening in the manual. Indoor-rated does not mean sealed: the heater is still unvented, so every bit of its exhaust and moisture stays in the room.
Even a certified heater needs three things from you: a window cracked to the opening the manual specifies, a working carbon monoxide alarm on that floor, and someone awake. Do not run one while the household sleeps, and do not rely on the sensor in place of the alarm. They watch different things.
Propane and fuel heaters that must never run inside a house
- Torpedo or salamander heaters. These forced-air construction heaters are built for open, unfinished buildings with air moving through them, and they have no oxygen sensor.
- Tank-top radiant heaters that screw onto a barbecue cylinder. Outdoor and job-site use only.
- Barbecues and patio heaters. High output, open flame, no safeties suited to a room.
- Camp stoves and lanterns, which are sold for tents with the flaps open and for picnic tables.
- Kerosene heaters. Different fuel, same carbon monoxide risk, plus fuel spills and fumes when refilling.
Where the propane cylinder can and cannot be
Ontario adopts CSA B149.2, the propane storage and handling code, and it restricts cylinders inside dwellings. The practical rule for a homeowner is short: a 20 lb barbecue cylinder is never stored or used in a house, a basement or an attached garage. It lives outdoors, upright, away from doors, windows and dryer vents.
The reason is physical. Propane vapour is heavier than air, so a leaking cylinder indoors does not disperse; the gas runs along the floor, down the stairs and into the basement, where it collects around the floor drain and the water heater burner. Indoor-rated portable heaters are designed around the small 1 lb cylinder for that reason. Change cylinders outdoors, keep spares out of the living space, and never refill a disposable cylinder.
Rules while the heater is running
- Set it on a hard, level floor with the clearances in the manual, usually well away from bedding, curtains and furniture.
- Keep the window open the stated amount for the entire time it burns, even though it feels like letting the heat out.
- Test the carbon monoxide alarm before you light the heater.
- Shut it off and leave the room if anyone gets a headache, feels dizzy or nauseous, or the flame turns yellow and sooty.
- Turn it off before bed and before leaving the house.
If the alarm sounds, the steps are in what to do if a carbon monoxide alarm goes off. An electric space heater in one closed room is the lower-risk stopgap wherever the power is on, and a kitchen range is never one: see whether you can heat a house with the oven.
Rural homes that already heat with propane
Past the end of the Enbridge Gas mains, in rural Caledon, Lowville, Kilbride, Campbellville, Carlisle and rural Flamborough, the furnace itself often runs on propane from a tank in the yard. When that furnace quits, the fuel supply is rarely the fault, and the yard tank is not a source for a portable heater: do not run a hose from it or from a barbecue cylinder through a window. If the tank ran empty, have the supplier refill it and put the appliances back in service.
In a power outage, a portable generator can keep a gas or propane furnace running if it is connected properly, which beats any room heater; running a gas furnace on a generator explains how. The generator stays outdoors for the same reason the barbecue does.
A portable heater buys a few hours, not a winter. ZK Mechanical repairs natural gas and propane furnaces, and its technicians hold TSSA gas licences. Reach the emergency heating service at (647) 801-1252 day or night, ask for a repair visit online, and if the house has no alarm on every level, carbon monoxide detector installation can be done on the same trip.