Can You Sleep in a Vehicle with the Windows Closed?

After a long journey by car or just a lot of time spent sitting in a car it is highly tempting to kick that seat back and grab a little shut-eye. While more or less comfortable, having a snooze in your car might not be a good idea owing to various safety concerns, especially with the windows rolled up. Everyone seems to have a different opinion on this.

Can you sleep in a car with the windows closed? No, you should never do that, regardless of whether the windows are open or closed. If the engine is running, carbon monoxide could build up due to a sealing failure, or exhaust system blockage. This can result in carbon monoxide poisoning that can make you gravely ill… or worse.

Sleeping in a car is something that most people have done at some point or another in their life, and it might be the only reasonably safe option you have when on the road. That being said, it would be a tragedy to die stupidly from not understanding all the risks involved.

In the remainder of this article will provide you with several considerations that can help you decide when and under what circumstances you should sleep in your vehicle with the windows up.

Carbon Monoxide Can Accumulate in the Passenger Compartment

Unless you are taking a nap in your convertible that has the top down or you have all of the windows all the way down in your vehicle, there is always a chance that exhaust emissions from a running engine may result in carbon monoxide buildup in the passenger compartment.

This typically occurs as a result of the tailpipe or tailpipes being blocked by snow, water or some other obstruction, or due to faulty maintenance allowing exhaust admissions into the cabin. This could result from something as simple as degraded sealing on doors or around the firewall.

The only way to prevent either of these from happening is to remain vigilant, and stay on top of maintenance.

Tailpipe obstructions can be prevented by paying attention to where you are parking and also taking care of periodically to keep the tailpipe clear in case snow or some other debris is accumulating near it.

Carbon monoxide buildup due to malfunction or other damage can be detected and corrected by periodic and thorough maintenance.

Naturally carbon monoxide build-up can be avoided completely if you don’t have the engine running while you are inside the car with the windows up.

Carbon Monoxide is Dangerous!

Exhaust gases that find their way into the cabin while you are taking a nap are more than just an air quality hazard. Exhaust gases contain significant amounts of carbon monoxide, a deadly airborne poison and one which is a leading cause of death in many countries around the globe.

Though you might smell significant accumulations of exhaust, you might not and you don’t have to smell it for carbon monoxide to be building up. Carbon monoxide has no color, no taste and is completely odorless on its own.

Even if the exhaust is leaking in significantly while you are asleep, you might not be roused in time to save your own life.

As carbon dioxide accumulates in the body, it bonds with the hemoglobin in the bloodstream. This in turn prevents the hemoglobin from carrying oxygen to the other organs in your body. In essence, it is starving your body of oxygen even though you are breathing normally.

Symptoms vary a little bit from person to person, but will steadily progress, getting worse and worse as more carbon monoxide is inhaled.

Typical symptoms of low to moderate dose carbon monoxide poisoning include vomiting, headache, dizziness, nausea, tiredness and muscle weakness. More significant symptoms indicative of serious carbon monoxide poisoning include everything from syncope and seizure to pronounced confusion and even visual aberrations.

It is very common for victims of carbon monoxide poisoning to mistake such for some other sickness such as the flu, common cold or even food poisoning.

Many victims of carbon monoxide poisoning succumb to it while they are asleep, arousing too late to affect self rescue. Many victims who die from it do so in their sleep, never waking up.

Slightly Opening the Windows is not Enough

Chances are you’re familiar with the dangers posed by carbon monoxide already, and so are other drivers. Unfortunately, quite a few drivers believe it is safe to take a nap inside their vehicle as long as they crack a window or two to allow fresh air in.

This is well-intentioned as ventilation is important for dispersing carbon monoxide but is ultimately misguided.

Keeping the windows open slightly, even all of them, will provide for some additional ventilation but generally cannot be relied upon to move enough fresh air into the vehicle to disperse or reduce the concentration of carbon monoxide.

If a dangerous condition exists inside the vehicle with the windows all the way up it will still exist with the windows slightly open.

The Air Conditioner is Similarly Ineffective

Similar to cracking the windows above, some motorists believe turning the AC on full will draw enough fresh air from the outside to keep the interior of the vehicle safe while the engine is running.

This is only adequate if a trace amount of carbon monoxide is accumulating in the cabin, because the air conditioner does nothing, typically, to cycle air out of a sealed cabin.

Once again, the only way to ensure that the interior of your vehicle will remain free of carbon monoxide build-up if you choose to sleep inside it with the windows up is to turn the engine off. Anytime exhaust gases are present the risk of carbon monoxide accumulation exists.


Sleeping inside any vehicle while the engine is running and the windows are up is not a good idea. Carbon monoxide may accumulate inside the passenger compartment due to an influx of exhaust gases, I know the chances of this occurring are generally small the consequences can be severe, even fatal.

You should never, ever sleep in a vehicle with the windows closed and the engine running. If you must sleep in your vehicle and keep the windows rolled all the way up, shut the engine off.

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1 thought on “Can You Sleep in a Vehicle with the Windows Closed?”

  1. The danger is far greater than anyone will or can ever tell you. I have see two instances of carbon monoxide poisonings. one killed my friend and his new girl friend. Christmas! out celebrating both Christmas and my birthday. having a good time but I had to go to work the next day so I needed four hours of friend borrowed my car to drive his girl home because it was colder than the proverbial well diggers A_ _. he was to leave the keys in my mail box when done. because the car was in the garage they started to make out and got cold and started the car. because they were ready to go. as I an many others know time is lost when you are with someone you like. it took four minutes and they knew they were in trouble. she had got her door open and had her feet on the floor and was overcome just laying back on the seat. my friend was trying to get his door open. they died that night. I found them in the morning when I looked for my keys and saw the interior lights on inside my garage. I lived across from a fire department and they came quickly but they couldn’t save them. this isnt just a scary story, it was real and they both died. two lives with potential. he just back from Nam making arrangements for to pick up where he left off with life. what the enemy couldn’t do in two years a mistake made because of a distraction caused them their lives. teach your kids about the dangers and how quickly it will kill you. the other event had a better ending. my friend was working on his car. having an exhaust leak and trying to find it was under the car while running. his mother called him for lunch and got no answer. she went to tell him again and found him unconscious. He also had the door closed but had the small entry door open. this gas doesn’t care who you are nothing matters more than your life. talking about death isnt pleasant and if it causes your child a nightmare then it should be. protecting them for a moments discomfort isnt worth the cost of their life. you can make only one fatal mistake.—————Grampa


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