Why leaving alcohol bottles inside your car is a bad idea

Updated Oct 01, 2020 | Same topic: Automotive FYIs

It’s better to take it with you after parking your car.

During the length of the quarantine caused by the spread of the COVID-19 pandemic, many car owners have undoubtedly turned to stash bottles of isopropyl alcohol in their vehicles. A bottled rubbing alcohol is after all more convenient than using soap and water especially when you’re out on the road. Just open the bottle, dab your hands with it, rub for around 20 seconds, and you’re good to go. Some even use alcohol for cleaning their car’s steering wheel, gear shift lever, and parking brake.

A picture of a bottle of hand sanitizer.

You can still bring a bottle of alcohol or hand sanitizer, just don't leave it in your parked car

That’s all well and good. However, leaving a bottle of rubbing alcohol inside your parked car is not a good idea, according to the Food and Drug Administration of the Philippines. 

Why you shouldn’t leave isopropyl alcohol inside your car

As implied by numerous social media posts both locally and abroad, alcohol will explode when left in a hot enclosed space like the interior of a parked car. Moreover, the posts are saying that a bottle of alcohol shone directly by refracted sunlight might explode. 

A picture of a car with damaged window caused by exploding bottle of alcohol.

A broken car window and damage to the interior allegedly caused by an exploding bottle of alcohol

The Center for Disease Control also says that alcohol and alcohol-based sanitizers evaporate quickly even at room temperature. If you want to get technical, the flashpoint of isopropyl alcohol is much lower at only 13 degrees Celsius if its container is open.

As such, fumes of evaporated alcohol will collect inside your car. Those fumes can be flammable, although it will not combust without a spark.

Furthermore, most alcohol bottles themselves actually have a warning label regarding its proper storage. It states that the bottle should be closed properly in a place with a temperature not exceeding 30 degrees Celsius. To this end, an improperly closed alcohol or sanitizer bottle might allow for the alcohol to evaporate. 

Note however that isopropyl alcohol has a pretty high auto-ignition temperature of 398 degrees Celsius. In other words, that’s the temperature it would need to spontaneously combust.

>>> Related: Keep a close watch on 6 main reasons causing car fires

A picture of a car interior fire damage.

Fires caused by alcohol-based products are still a possibility just like this

To sum it up, your alcohol bottle will not spontaneously combust inside your hot car. However, one should also remember that alcohol shouldn’t be stored in high-temperature places in the first place.

So what happened to the pictures above? Due to the heat from the refracted sunlight, the vapor inside the alcohol bottle might have expanded. As such, there was a build-up of pressure. This might have caused the alcohol bottle to turn into a small rocket ship, slamming within the car thus causing damage. Note though that if this was the case, then this can also happen to water bottles.

The alternative

No, we’re not telling you to stop carrying bottles of isopropyl alcohol or hand sanitizer around with you in your car. In fact, we encourage you to do so. As we’ve said, using these products is among the most convenient ways of keeping yourself safe from COVID-19.

A picture of a woman cleaning her car using alcohol spray.

Plus, it's just convenient to use alcohol to disinfect your car's interior

Instead, we highly advise car owners to bring with them their bottle of alcohol or hand sanitizer once they parked their cars, especially when the parking space has no shade or roof. Sure, your pocket or handbag might be heavier, but that inconvenience is nothing compared to finding your interior torn up.

We’re not trying to scare you or be alarmist, but the warning from FDA is already out. Regardless of whether a bottle of alcohol or sanitizer will explode or not, we’re just relaying this to you to keep you and your car out of harm’s way. It’s better to be safe than sorry folks.

>>> Related: Home and Fire Insurances in the Philippines: What’s the Difference?

Alcohol Bottles inside a car: FAQ

1. Question: Does hand sanitizer contain isopropyl alcohol?

Answer: Yes, most hand sanitizer brands have 75 to 80 percent alcohol content.

2. Question: How hot would it need to be for isopropyl alcohol to spontaneously combust?

Answer: The auto-ignition temperature for isopropyl alcohol is 398 degrees Celsius.

3. Why is alcohol so flammable?

Answer: Alcohol is generally flammable because it is made up of molecules that contain a lot of chemical bonds, which in turn means a lot of potential energy.

4. What do I do in case of a fire caused by alcohol?

Answer: The best way to put out an alcohol fire is to smother it with a reasonably heat resistant material. If available, you can use a chemical fire extinguisher. Using water can potentially spread a flame fueled by alcohol so don’t use water.

5. Are alcohol fumes flammable?

Answer: Isopropyl alcohol vapor is flammable.

For more safety tips relating to car ownership, keep reading here on Philkotse.com.

Cesar G.B. Miguel

Cesar G.B. Miguel


Cesar Guiderone B. Miguel was born and raised in Iligan City, Lanao Del Norte. He graduated in 2010 with a Bachelor of Arts in English degree from Mindanao State University - Iligan Institute of Technology. He previously worked as a freelance writer for various websites, as a member of the Iligan City Disaster Risk Reduction Management's training staff, and as a medical sales representative.

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