Dig out the tailpipe before you run the heater
Stranded in snow, the engine is your heater and your danger. Clear a wide space around the tailpipe, run it ten minutes an hour, stay put.
Drawn from people's advice about what to keep in the car for winter and how to wait out a breakdown in the cold, checked against US CDC and National Weather Service guidance and a study of carbon monoxide in a snow-blocked car.
Stuck in the snow, the car feels like the safe place, and mostly it is. The engine that heats it is also the thing that can kill you in it, and a window open a crack does not protect you the way it seems to, and nor, one person points out, does the button that recirculates the air.
Before you run the engine for heat, clear the snow from around the tailpipe all the way to the ground; then run it about ten minutes in each hour with a window open slightly, check the pipe each time, and stay awake.
The tailpipe, and what does not protect you
Some people give the rule: when you run the engine to keep warm, make sure the exhaust pipe is clear of snow, or carbon monoxide comes into the car. One person sharpens it. A blocked exhaust can stall the engine, it says, but the killing part is the gas finding its way into the cabin through the air intake when it has nowhere else to go. Another account, from experience, says a loud exhaust can mean a break in the pipe that fills the cab with fumes — a leak does the same thing with no snow at all. The CDC recommends having the exhaust system checked by a mechanic every year for that reason.
What real tests add is how much “clear” means. In a study published in 2004, researchers shovelled snow around a car to the level of its bumpers, ran the engine and measured the air inside. With the windows shut, carbon monoxide reached the top of their meter within two and a half minutes. With the front windows open an inch, and then six inches, it still reached dangerous levels within five minutes, and seven and a half. With the tailpipe swept clear but the snow still banked around it, it was little better. The car was safe only when the snow was cleared from a space about twelve inches wide, all the way to the ground.
So the window open a little is for fresh air, as the CDC and the Weather Service both advise, and it is not protection. One person makes the same point about the recirculate button: setting the fan to recirculate does not seal the car, and exhaust can still get in through the gaps. This page found no test of that, and the study above suggests treating nothing inside the car as protection — only a clear pipe, checked each time you start the engine.
Stay with the car, and ration the engine
Some people say stay inside: the car is shelter from the wind, and it is what rescuers will see. The Weather Service is blunt about why — leave the car in wind-driven snow and you become disoriented quickly — and the CDC says staying is often the safest choice when visibility is poor or the roads are iced. One person makes the judgement explicit from the other side: in a town, in clear weather, walking a short route you know to a warm building can be the right call. A storm on an open road is not that.
Run the engine for about ten minutes in each hour, the CDC and the Weather Service say, not all the time. That rations the fuel and cuts the time the exhaust is working against you. Some people say to keep at least half a tank all winter; the US authorities go further — near full, the Weather Service says, which also keeps ice out of the fuel lines — and one person says to treat half a tank as empty. Plan for the engine stopping, one warning here says, and do not let the heater be your only way to keep warm. One question people ask is whether it is fine to nap with the engine running; one person says yes, if you have the fuel. This page does not carry that. The CDC says stay awake, and warns that people who are asleep can die of carbon monoxide before they have symptoms.
Staying warm while you wait
Many people say to keep blankets, a sleeping bag or spare coats in the car, because when the engine is off, your own body heat is what you have left. Three recommend a sleeping bag. In one conversation some people say a big blanket does the job and two prefer the bag, and one person gives the practical reason — a blanket is hard to keep wrapped around you sitting in a seat, and a sleeping bag covers your head too. Many people add gloves and a hat, and point out that gloves also save your hands from cold metal if you have to touch the car or its tools. A wet blanket is worse than none, one person warns, and a foil emergency blanket packs small.
The CDC adds three things worth doing: keep moving your arms and legs as you sit, huddle with anyone else in the car, and stay awake. One person says to get wet socks and shoes off at once, before they bring on frostbite; another warns against taking your shoes off at all, because they are part of what keeps your feet warm. They disagree about the shoes; both want your feet dry, which is a reason to keep spare socks in the kit. Cotton socks hold water and stop insulating, another says; the page called What actually keeps you warm outside explains why cotton is the problem, and which clothes are not.
Being found
Help has to see you. The Weather Service says turn the dome light on at night while the engine is running, tie a bright cloth — red is best — to the aerial or a door, and once the snow has stopped, raise the bonnet as a sign you need help. One person points out that a white car is hard to see in a blizzard, which is one more reason for the cloth. Some people add flashlights, flares or road reflectors set well behind the car. Keep the phone charged; people disagree about how — a separate battery pack is independent of the car, but loses charge sitting unused for months, while a charger that plugs into the car needs the car’s battery to be alive. And one person suggests saving your local police non-emergency number before winter, so you are not searching for it in a snowbank.
Who this page is not for
If you can still move the car and are trying to get unstuck, the page called Spinning digs the hole deeper is the one you want; this page is for the wait. If you, or someone with you, is shivering, exhausted, confused, fumbling, slurring or drowsy — the CDC’s signs of hypothermia — or has numb, white or waxy skin, the signs of frostbite, get medical help as soon as you can: 911 in the US, 999 in the UK. If the car is buried so deep that you cannot open a door, this page does not cover what to do; call for help and keep the tailpipe question in mind before you start the engine. And one person makes the point for anyone who lives somewhere mild: a breakdown on a cold night can catch people who never think of themselves as living in snow country.
Common questions
Does a candle really help?
It can, and it is on the US National Weather Service’s own winter car list: a candle and matches, for light and, in an emergency, lifesaving heat. The argument is about how much. Some people say a candle raises the temperature in a car enough to keep someone from freezing, and one person says candles and an emergency blanket got them through a breakdown in extreme cold. Others answer that the physics make the heat small, and that a candle is mostly light and comfort; one person says a single candle did nothing they could feel at around -10°C, and another replied, try two. Both can be true: a candle will not make a car feel warm, and in a long, cold wait a small amount of heat still counts. If you use one, the conditions people attach are the whole point. Stand it in a metal can, so it cannot tip and the can throws back some heat. Keep it well away from blankets, clothes and sleeping bags, and never light one inside a blanket. Not on the dashboard, one person warns, where the heat can crack the windscreen. Open a window a little, because anything burning in a closed car gives off gases you do not want to breathe; one person adds that the fear of a candle using up the oxygen is unfounded, so the reason for the gap is the fumes, not the air. And carry more than one, and the lighter to go with it: newer cars often have no cigarette lighter, one person points out, so bring your own flame. One idea here — a homemade stove of a can, paper and rubbing alcohol — this page does not carry: its own accounts warn that alcohol flames can be invisible and dangerous if tipped, and that you should never add alcohol to a flame.
What about water and food?
Many people say to carry both, and to not eat snow. The CDC gives the reason: eating snow lowers your body temperature. Melt it first — the Weather Service’s list includes a small can and waterproof matches for exactly that — or, as one person suggests, pack clean snow into a bottle and hold it under the blanket with you, where your own warmth melts it. Water in the car freezes, so some people say to leave room at the top of every bottle; a full one can split when it freezes. One person points out that plain water will freeze solid in a cold car, one person says to swap it once a season, and another says glass bottles are a bad idea in a car at all. On food, one person argues you will not starve in a ten-hour wait; others answer that hunger and thirst make you think worse and feel worse, and that the wait may be longer than you planned. Calorie bars and anything else that needs no cooking — and swap out the sweets in summer, one person adds, before they melt.
What should the kit actually hold?
The US National Weather Service’s list for the car is the plain answer: a phone and charger; blankets or sleeping bags; a flashlight with spare batteries; a first-aid kit; a knife; high-calorie food that keeps; extra dry clothes; a large empty can to use as a toilet, with tissues and toilet paper; a small can and waterproof matches to melt snow; a sack of sand or cat litter for grip; a shovel; a scraper and brush; a tool kit; a tow rope; jump leads; a water container; a candle and matches; and a map and compass, because a phone battery runs out. Others add daily medicines, spare socks, a change of clothes, a little cash, and reflectors to set far behind the car. On the grip: some people say the litter must be the non-clumping kind — clumping litter turns to a slippery paste when wet — and another says sand grips better than litter. One person says to put it down before the wheels start spinning, not after; another, under both drive wheels. How to use it to get out is on the page called *Spinning digs the hole deeper*. Some people warn against storing a sleeping bag squashed in its sack all year, which ruins the fill; hang it or lay it loose. And one person suggests practising fitting snow chains in the garage, because doing it for the first time beside a frozen road is hard and dangerous. Keep the kit in a box in the car, out of sight.
Questions this step helps with
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