Pequea Valley HS Semi-Virtual Commencement

Hand sanitizer at the ready, as seniors participate in a semi-virtual commencement at Pequea Valley High School in Kinzers Tuesday May 26, 2020.

After a Facebook post about hand sanitizer catching a car on fire went viral, people are asking: will alcohol-based hand sanitizer left in a hot car cause it to ignite?

Many were skeptical in the comments section, saying that Cathy Pagendarm was "fearmongering" and spreading false news. But it became trickier when the Western Lakes Fire District in Wisconsin posted a similar (now deleted) photo, confirming what Pagendarm shared.

Though alcohol-based hand sanitizer is flammable, the chances of it catching fire in the car are minimal, says the National Fire Protection Association. 

In a Facebook video, the NFPA said that temperatures in the car would have to reach over 700 degrees to set the hand sanitizer on fire without a direct fire ignition.

A flame would easily hit 700 degrees Fahrenheit, but the inside of a car would not.

The WLFD has since redacted its stance that alcohol-based hand sanitizers could ignite in a hot car. The fire company says it posted about hand sanitizer containers causing fires because sunlight passing through clear containers is a real fire hazard. 

"While infrequent, there have been cases in the recent past were reflecting light placed through a clear bottle was able to focus onto a combustible surface and cause a fire," the fire department said on its Facebook page. "This has primarily been through water bottles but since hand sanitizer is often stored in the same vessel we wanted to pass it along for your safety."

Experts recommend that you don't keep hand sanitizer in the car, however. But not because of the fire risk. 

Dr. Greg Boyce, a professor at the Florida Gulf Coast University, told ABC that if hand sanitizer were kept in the car for more than a few hours, the alcohol could evaporate, making the sanitizer less effective.

USATODAY created a full fact-checking guide on hand sanitizer and hot cars.

The consensus? Leaving sanitizer in your car will likely not cause a fire. But, don't leave it in your car if you want to make sure it keeps its potency.

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