Fuel-burning heaters, generators and carbon monoxide in the cold months

Every winter the same things come out of sheds and garages. The generator that has sat under a tarp since the last storm. The paraffin heater someone's father swore by. The camping stove, the patio heater, the bag of charcoal left over from summer. Each of them burns fuel, and anything that burns fuel can make carbon monoxide, the gas you cannot see, smell or taste. In the cold months the danger is not the appliance itself so much as where we are tempted to put it: indoors, in the garage, in a closed room with the windows shut against the weather.

This piece goes through the usual winter sources one at a time, with the advice the official bodies give for each, and then works through a power cut evening the way I would handle it. It sits alongside our guide to carbon monoxide alarm placement, which covers where alarms go and how to test them.

Where the winter carbon monoxide comes from

Fuel produces carbon monoxide when it does not burn properly, usually because there is not enough air or because the fumes have nowhere to go. In a house that means a few familiar suspects:

None of these is unusual. Most homes have two or three of them within reach.

Portable generators: outside, and well away

The generator is the one I worry about most, because it gets used in a hurry, in the dark, by someone who has not read the manual since they bought it. The advice from the CDC is simple: run it outdoors, more than 20 feet (about 6 meters) from windows, doors and vents, and never inside the home or garage, even with the doors and windows open. CPSC says the same about homes and garages. NFPA adds that the exhaust should point away from the building so fumes cannot drift in through an opening, and that you should never run a generator in an attached garage, even with the door open.

An open garage door feels like plenty of air. It is not. The exhaust from a small engine fills the space faster than it clears, and an attached garage shares walls, doors and sometimes ductwork with the house.

A few more points from the NFPA generator tip sheet that I keep in mind:

• Turn the generator off and let it cool before refueling. Never refuel it while it is hot.
• Store its fuel in a container made for that fuel and labeled as such, outside the living areas of the home.
• Make sure CO alarms are fitted in the house, following the maker's instructions for placement and mounting height. The CDC suggests a battery-operated alarm or one with battery backup when you use a generator, since the mains may be off.

Paraffin and kerosene heaters

Paraffin in the UK and kerosene in the US are the same family of fuel, and portable heaters that burn it are still common in sheds, workshops and older homes. CPSC publishes a safety alert on them, and the main points are worth having on a card beside the heater:

• Use only water-clear 1-K grade kerosene. Never use gasoline (petrol), and never let it near the heater. CPSC notes that even small amounts of gasoline or other volatile fuels mixed in can make a fire or explosion much more likely.
• Store the fuel in a container meant for kerosene, not a petrol can or one that ever held petrol. CPSC notes that kerosene cans are usually blue and gasoline cans usually red, and that kerosene should be stored away from other fuel containers.
• Never refuel indoors. Fill the tank outside, away from anything that can burn, only after the heater is off and has cooled. Do not fill above the full mark.
• Run the heater in a room with the door open to the rest of the house. CPSC suggests opening an outside window about an inch if the door has to be closed or the house is very airtight.
• Keep the wick clean and set at the level the manufacturer gives, and keep the heater at least three feet from furniture and clothing.

In the UK the same habits apply. If your heater came with a manual, keep it with the heater; it will say what fuel it takes and how the wick should be set. NFPA's heating advice puts it in one line: always use the kind of fuel the manufacturer specifies.

Flues, chimneys and vents

The fixed appliances do most of the heating, and they cause trouble when the route out for their fumes is blocked. CPSC urges a yearly professional inspection of all fuel-burning heating systems, including furnaces, boilers, fireplaces, wood stoves, water heaters, chimneys, flues and vents. The CDC and NFPA say much the same: have heating equipment serviced and chimneys checked every year, ideally before the cold weather starts. In the UK, the NHS advises having boilers, heaters and cookers serviced by a qualified, registered engineer.

Between services, there are things you can watch for. The HSE lists signs that a gas appliance may not be burning properly:

• yellow or orange flames where they should be blue
• soot, or yellow or brown staining, on or around the appliance
• a pilot light that keeps blowing out
• more condensation than usual on the inside of windows

If you see any of these, stop using the appliance and have it checked. In Britain, the HSE website lists the national gas emergency line to call if you suspect a gas appliance is leaking fumes.

Snow is the other winter problem. NFPA advises keeping vents for the dryer, furnace, stove and fireplace clear of snow during and after a storm, and making sure the exhaust pipe of a running car is not buried either. I walk round the outside of the house with a brush after heavy snow and clear every vent I know about, including the boiler flue at the back that nobody sees.

Things that should never come indoors

Some appliances are made for outdoors and only outdoors. The CDC, CPSC and NHS are all clear on these:

• Charcoal: never burn it indoors, in a garage, a tent, a camper or a van, for cooking or for heat. CPSC is explicit that this includes garages.
• Camp stoves and barbecues: not indoors and not inside a tent. The CDC also says not to use portable flameless chemical heaters indoors.
• Gas ovens and ranges: never use them to heat the house. NFPA's line is that ovens are for cooking only.
• Cars and trucks: never leave one running in an attached garage, even with the door open. If you need to warm the car, NFPA says to back it out of the garage straight after starting it.

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A power cut evening, worked through

Here is how I would run the evening when the power goes out on a cold night, in a house with an attached garage, a portable generator and a paraffin heater in the shed.

1. Torches first, not candles, and check the CO alarms have battery power. If an alarm is plug-in only, it is off with the mains.
2. Carry the generator out of the garage to a spot on the far side of the yard, more than 20 feet from any window, door or vent, with the exhaust pointing away from the house and from the neighbor's house too. If that spot is under a window you do not normally think about, such as a basement window or a bathroom vent, move it further.
3. Run an outdoor-rated extension lead back to the house for the fridge and a lamp. Do not prop the garage door open to feed the cable through and then leave the generator inside.
4. Fill the paraffin heater outside, while it is cold, with the right fuel from the blue can. Bring it into the living room, leave the door to the hall open and a window open about an inch, and keep it three feet clear of the sofa.
5. Leave the barbecue and the camping stove where they are. Cold food is a better evening than a stove in the kitchen.
6. Before bed, turn the heater off. CPSC advises against using portable heaters while sleeping in enclosed areas such as tents and campers, and I apply the same rule at home.
7. Refuel the generator only after it has stopped and cooled, outside.

If an alarm sounds

Do not go looking for the source. Get everyone out of the house into fresh air, pets included, and call the emergency number from outside: 911 in the US and Canada, 999 in the UK, 112 across the EU. NFPA advises staying outside until emergency services say it is safe to go back in. If anyone is unconscious, having trouble breathing or having a seizure, tell the call handler at once.

The same rule applies to any product in the shed or garage. If someone may have swallowed, breathed in or splashed a fuel or other product, call your local emergency number or a poison center now, with the container or its label in your hand. In the US, Poison Help is 1-800-222-1222. In the UK, call NHS 111, or 999 in an emergency. In the EU, the emergency number is 112. Our official help page lists where to find other contacts.

Common questions

Is it all right to run a generator in the garage with the door open?

No. The CDC, CPSC and NFPA all say never, even with doors and windows open. Outside, more than 20 feet from openings, exhaust pointing away.

Do I need a CO alarm if my only fuel-burning appliance is a heater I use a few nights a year?

Yes. Those few nights are exactly when it matters, and the official advice is to have alarms near sleeping areas and on every level. The safety shelf lists the kinds of alarms we write about.

Can I use a patio heater in a garage with the door open?

They are made for outdoor use. Treat one the way you would a barbecue: outside, in open air, and never in a garage, tent or porch with the sides down.

The CDC's carbon monoxide basics and CPSC's page on portable heaters and camping equipment cover these points in more depth. Before the first cold night, take ten minutes to read the manuals for the heater and the generator, then put them in a plastic bag tied to the handle, where the next person to need them in the dark will find them.