Can hand sanitizer catch fire in a hot vehicle?

Posts shared thousands of times on social media in May 2020 show a photo of the melted inner panel of a car door claiming it is the result of a hand sanitizer fire.

The posts claim that the gel ignited after being left in a hot car. The claim is misleading. According to fire experts, alcohol-based sanitizers are flammable, but it is “highly unlikely” for them to spontaneously combust.

“The photo below is from hand sanitizer igniting in a hot vehicle that reached 35 deg C. inside the vehicle,” claims a post shared 15,000 time since May 14, 2020.

A reverse image search of the picture shows that these claims have also been published in Portugese. The claim circulated in French (1,2,3,4) and has been fact-checked by a number of Brasilian outlets (1,2,3).

However, Toronto Fire Services said on Twitter: “Hand sanitizer won’t spontaneously combust or explode if left in a hot vehicle.”

1. Is it safe to leave hand sanitizer in a hot vehicle?

Hand sanitizer wont spontaneously combust or explode if left in a hot vehicle. Containers should be kept upright and properly sealed to avoid leakage. Containers shouldn't be left in direct sunlight as an added precaution pic.twitter.com/4W1uerTTzg

— Toronto Fire Services 🇨🇦 (@Toronto_Fire) May 26, 2020

The same guidance was shared on Twitter by the US National Fire Protection Association and the Richmond Hill Fire Service in Ontario, who recommended keeping the bottles upright and out of direct sunlight.

The post claims that the hand sanitizer ignited in a vehicle that reached 35 degrees Celsius (95 Fahrenheit).

“Highly unlikely,” Larry Cocco, Deputy Fire Chief at Toronto Fire Services said.

Flammability

Several hand sanitizer products researched by AFP are marked flammable.

Health Canada requires that alcohol-based hand sanitizers carry a flammability warning: “Keep away from open flame and sources of heat.”

Flashpoint

The post correctly claims that hand sanitizer has a relatively low “flashpoint”.

The “flashpoint” is the point at which the liquid starts to “produce vapors” that could catch fire, according to Cocco.

Hand sanitizers are usually composed of around 60 to 70 percent ethanol or isopropyl alcohol, according to Cocco. The US National Center for Biotechnology Information says the flashpoint for ethanol is 55 F (12.8 C) and 53 F for isopropyl alcohol.

The post goes on to describe flashpoint as “Ignition/flame”. This is misleading.

Hand sanitizers are most commonly used in bottles with a cap or a pump, so the vapors are contained and cannot find an ignition source.

If the liquid were stored in an open container in a car, it could theoretically produce vapors.

However, “you still need an ignition source,” and Cocco says “parked cars really don’t have a lot of ignition sources.”

Cocco adds that the only way the vapors could breach a closed bottle “is if it reaches boiling point, which is very high, on average 80 degrees Celsius.”

He further explained that the hand sanitizer would have to reach 400 C to “auto-ignite”.

Avoid unnecessary risk

The US Centers For Disease Control and Prevention recommend the use of hand sanitizer with at least 60 percent alcohol if soap and water are not available, to “help you avoid getting sick and spreading germs to others.”

Toronto Fire Services add: “When using hand sanitizer, hands should be rubbed together until they are completely dry. People should be especially careful if attempting to smoke, light candles, or use a gas stove immediately after applying hand sanitizer.”