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How Long Can You Sleep in a Car Before Suffocating?

Driving can be exhausting, and sometimes you need to pull over and get some rest on a road trip. While sleeping in your car may not be the most comfortable, it’ll get the job done in a pinch.

However, you’ll need to remember some safety concerns while sleeping in your car. Ever wondered how long you can sleep in a car before suffocating? Let’s find out.

Can You Suffocate Sleeping in a Closed Car?

Vehicles aren’t airtight, so you won’t suffocate by sleeping in a closed car. If cars were airtight, we wouldn’t have nearly as many vehicles sitting on the bottoms of rivers and lakes. The vehicles would float and would be easy for rescuers to pluck from the water.

One study from the National Library of Medicine even found that a car sitting stationary replaces all of the air in several hours. It would take cramming nine individuals into a standard-size vehicle before there were any adverse effects while sleeping in a car.

The risks of suffocating in a closed car are practically zero. However, a larger concern about sleeping in your car comes from the temperatures, which could cause heat exhaustion.

How Long Can You Sleep in a Car Before Suffocating?

It is not possible to suffocate while sleeping in a car. You have plenty of oxygen, and the air inside your vehicle will cycle through the air vents every few hours. 

You would need to cram substantially more people into a vehicle than it would normally hold before running out of oxygen would become a concern.

Should You Crack a Window When Sleeping in Your Car?

While you don’t have to worry about running out of oxygen, sitting in an enclosed vehicle can get uncomfortable. Cracking a window or two can increase air circulation and remove the stuffiness that often occurs in these situations.

If you have multiple people sleeping in your car, it will be more beneficial to crack a window or two. The more people, the stuffier the vehicle. However, only crack the windows and don’t roll them down completely for safety reasons. You don’t want someone to reach into your vehicle.

Pro Tip: If you’re going to car camp, make sure you know Where You Can Sleep in Your Car (Without Getting into Trouble?).

Woman sleeping on steering wheel in car
Sleeping in your car can be a good option if you’re feeling tired while on the road or simply want to camp for free.

How to Sleep Safely in Your Car

Safety is one thing that you should always take seriously, no matter what you’re doing. Here are some things you can do to sleep safely in your car.

Crack the Sunroof or a Window

Cracking a window or sunroof can be a great way to increase air circulation while you sleep. However, this can also lead to the potential of mosquitos and other insects finding their way inside.

Cracking the windows opposite one another in your vehicle can help create a cross breeze, especially if there’s a little wind outside. 

If this isn’t enough to keep air moving in your car, you may need to purchase some small battery-operated or rechargeable fans to help increase circulation or keep you cool.

Don’t Sleep With the Windows All the Way Down

You never know who or what may wander around your vehicle while you sleep. Leaving your windows down is extremely dangerous and leaves you unprotected. 

While you should have your windows down, you want to avoid lowering them to the point that someone can reach into your vehicle. You don’t want to wake up and find someone rifling through your stuff.

Couple laying in back of car together sleeping
Lay your seats back and cover your car windows for a good night sleep in your car.

Lay Your Back Seats Flat

Some vehicles have back seats that lay almost completely flat. While it might not be as comfortable as a pillow-top mattress, it beats trying to sleep sitting upright in your seat.

If you plan to sleep in your vehicle regularly, consider making a sleeping platform or modifications to make it as comfortable as possible.

Those who drive a van or SUV will likely have plenty of space and potential for making modifications to help you sleep soundly in your car. You can find some pretty incredible car camping conversions in the nomad community.

DIY Window Coverings

Since you may end up sleeping in public, you still want some privacy. Creating DIY window covers can help increase your privacy and avoid uncomfortable glances as people walk past your vehicle.

You can also purchase Reflectix foil insulation and cut it to size for each of your windows. These work great because they’re lightweight and make it easier to control the climate inside your vehicle while providing you with privacy. They don’t cost too much, and you can easily store them when not in use.

Wear Layers If It’s Going to Be Cold

If you need to sleep in your vehicle in cold weather, wear layers while you try to sleep. Wear thick socks and a stocking cap, and consider putting on gloves. You can’t keep your car running with the heater on all night, so make sure to bundle up. 

It’s better to over-prepare for the cold and take off items than to find yourself underprepared and to shiver the entire night. You’ll likely find it hard to get any quality sleep in the cold.

Man sleeping in his car
Try car camping in a Walmart or Cracker Barrel parking lot.

What Is the Safest Place to Sleep in Your Car?

If you stay in an area that allows overnight parking, Walmarts and Cracker Barrels are some of the safest options. They typically have lights, security cameras, and enough traffic driving by that criminals will think twice about messing with you. However, other popular options include hospitals, fitness centers, and truck stops. 

Pro Tip: Unsure if car camping in a public space is right for you? Check out these 5 Reasons to Avoid Overnight Parking.

Is Sleeping in Your Car Worth It?

While your car isn’t a five-star hotel, it’ll do the job in a pinch. Sometimes you do what you must when you need to rest while traveling. 

Hotels and campgrounds can be expensive and difficult to get, especially if you only need a few hours of sleep before hitting the road. If you take the proper steps and do what you can to make it as comfortable as possible, it can work out great.

Discover the Best Free Camping Across the USA

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