Is It Safe to Sleep in a Running Car With the Air Conditioner on?

Naomi O'Colman

Is It Safe to Sleep in a Running Car With the Air Conditioner On final

Is It Safe to Sleep in a Running Car With the Air Conditioner On final

You know that running the air conditioner in your car or truck can be a great way to stay cool on hot summer days. But it might not be so great for you. Is it safe to sleep in a running car with the air conditioner on? If you have any concerns about the safety of sleeping in a running car with the AC on, this blog post is for you! Read more about how to keep yourself safe while you sleep when driving with AC.

The Short Answer

Sleeping with the AC on while the car is running is okay. However, when the car is idle, there are some potential risks to your health, especially CO poisoning, and your car battery & engine.

Is It Safe to Sleep in a Running Car With the Air Conditioner on?

For the majority of vehicle models, it is perfectly safe to sleep in a running car with the AC on. For the most part, all cars with automatic AC will enter what’s called an idle-off mode after a few minutes without any activity. This way, your car doesn’t waste gas while you’re sleeping and running unnecessary electricity.

  Can You Mix 5w30 and 10w30?

However, there can be some risks if your car does not go into this idle-off mode while the AC is on. For example, most cars manufactured in the last few years have a feature that’s called an internal combustion shut-off or ICV. This feature prevents the engine from idling and shutting off while you’re sleeping with the AC on.

Is It Safe to Sleep in a Running Car With the Air Conditioner on
Is it safe to sleep in a running car with the air conditioner on

While this feature might be nice when you’re getting ready to drive your car, it can pose a problem if you want to sleep in your vehicle for an extended period of time. The ICV feature and shutting off the engine while it’s running will prevent harmful emissions from occurring in your vehicle. But it also means that the engine will be on when you do wake up in the morning.

Some vehicles come equipped with an internal combustion shut-off or ICV system with a timer so that after a set amount of time, your car will automatically shut off. This is considered best practice in most vehicles when it comes to sleeping in a car when AC is on with the car running.

If your vehicle doesn’t come with a timer or if you prefer to manually shut off the engine yourself, you can still sleep in the car with the AC on. It might take a little bit longer to cool down at night, but you’ll be taking it easy and saving fuel.

Risks Associated with Sleeping in a Running Car With the AC On

There are times when sleeping in a running car can be dangerous and can lead to health problems. If you’re always in a rush and need to catch up on some zzz’s, sometimes it’s tempting to sleep in your car when you’re on the road. While sleeping in a parked car is safe if the AC is off, sleeping with the AC running can be unsafe and can even be deadly.

  Seized Caliper Symptoms and How to Fix Them!

Carbon monoxide poisoning

Carbon monoxide poisoning
Carbon monoxide poisoning

Poisoning carbon monoxide (CO) is something that most people don’t think about when they’re trying to get some shuteye in their vehicle. While CO is cumulative, meaning you can still be at risk while sleeping in a running car, the biggest health risks come from sleeping while the AC is running.

Sleeping in a car can be fatal due to carbon monoxide poisoning.

When you run your AC and your car idles for a few minutes while you sleep, carbon monoxide (CO) can enter your vehicle and cause serious damage to your vital organs. This type of poisoning can cause headaches, fatigue, dizziness, and even death. And it’s all because of the exhaust that’s produced by the engine when it runs while idle.

Remember that the amount of CO produced by your car is not just determined by how long you have the AC on. How many miles per hour you drive and what kind of outside air you let into your car also play a major role.

For example, if you live in a very urban area or on a busy street where there’s lots of traffic, the level of CO will be much higher than on a rural road with little to no traffic.

Electrical parts could break down

Electrical parts could break down
Electrical parts could break down

Additionally, the AC system is quite unhealthy for you. Even if your automobile is safely parked, your car may malfunction if the engine is left running while you sleep in it.

When you are sleeping in a car, these faults, such as draining the battery and a broken exhaust pipe or exhaust system, are likely to go undetected but could have a negative impact on your trip when you wake up. They might even add extra dangerous exhaust fumes to your car, which could cause brain damage.

  Dot 3 Brake Fluid: Everything You Need to Know

Tips & Tricks If You Have To Sleep In Your Car With AC Running

Sleeping in a car with AC running is a dangerous game that many take part in. Thus, how can we keep ourselves safe?

If you’re worried about the CO level produced by your car, you can try to minimize your time on the road. Try to drive through heavy traffic intersections or at night when there are fewer cars on the road. These are both great ways to reduce CO levels in your car.

If you think your health is at risk while sleeping in your car with the AC on, step outside and attempt to breathe fresh air.

Or you can buy a CO monitor, costing around $20, to easily detect any CO levels in your car. If it’s too high, you might want to reconsider sleeping in the car with the AC on. The best CO monitor is an electrochemical CO detector. It uses light bulbs to detect the levels of CO in your vehicle inside or out.

Another tip is that you can roll down the windows a bit and park your car with the exhaust pipe away from the wind to avoid car exhaust fumes.

Does Running The AC For Long Damage The Battery & The Car Engine?

Does Running The AC For Long Damage The Battery & The Car Engine
Does running the ac for long damage the battery & the car engine?

There is some truth to the fact that running the AC for long periods of time can damage your vehicle. There’s not a lot of information out on the internet, but there are sporadic forum posts and blog comments that offer conflicting opinions.

  High Mileage Oil Vs Synthetic Oil: When Should You Use What

One thing we can say for sure is that it’s never good to let your car idle for hours and hours on end. AC or no AC, will burn through gas and reduce your fuel efficiency. The same goes for your car engine; idling can burn through fuel and reduce your gas efficiency.

The one thing we do know is that the idling time and amount of time that your car spends idle can affect how your battery and engine operate and degrade over time. This is because they’re both made to support electrical components in an automobile; but when they’re not running for a prolonged period, they will fail.

Common Symptoms of Running the AC for Long Periods of Time

If you aren’t getting to sleep well at night and you keep hearing the clicking noise from your car’s engine, there’s a good chance that it’s because your car is sitting idle and not running. The clicking noise is common with many modern cars and can be the sound of the alternator or battery charger. This clicking noise can also be heard if your battery or alternator is out of voltage.

A Piece Of Advice On Sleeping In A Car

Besides harming your health and your car, sleeping in a car is banned in many states like Florida or Virginia. Thus, make sure that you check the law and regulations of your state before you decide to sleep in your car.

  What Are the Best RV Awning Lights?

While this one goes without saying, having a full tank of water is imperative if you’re going to sleep in your car overnight. It’s better to be safe than sorry, so have plenty of bottled or boiled water on hand just in case.


Sleeping in a car is not considered dangerous if you’re running the AC with a running car. However, if the car is idle, it’s time to get out with your health & battery at stake.

While sleeping in a car is not recommended, sometimes it leads to more extreme circumstances, especially when people are traveling for work or vacation. If you have no choice but to sleep in your car overnight, you’ll want to turn off the AC and run the engine instead. This will reduce the amount of CO that’s being produced in your vehicle.

Further Reading: