Can Hand Sanitizers Cause Your Car To Catch Fire?

Recent headlines have warned readers about leaving hand sanitizer in the car under the hot sun, which apparently led to cases of it combusting and causing injuries and fires. How true, though, are these cases? The short answer is: unlikely, but not impossible and not in the way you might think.

Hand sanitizers comprise a minimum of 70% alcohol (at least the effective ones do) and are undeniably flammable. But according to the US National Fire Protection Association (NFPA), it would take temperatures of over 370°C for alcohol to spontaneously combust. And there is nowhere on the surface of Earth that you can park your car for its interior temperature to reach that.

HOWEVER, most hand sanitizers are contained in a clear plastic bottle and this is where the danger lies. While it rarely happens, the plastic bottle can act as a lens that focuses the sunlight that comes in through the windows. When the light photons are concentrated onto one spot, eg. on your upholstery, it could very well cause melting and burning. And if a bottle of very flammable liquid or gel sanitizer is nearby, a small fire could very quickly turn into a big one.

So, it would take a series of coincidences—sunlight shining just so through the plastic bottle, the focused light directed onto a flammable material and the bottle of hand sanitizer placed nearby—for your car to turn into a fireball, but it is not impossible. Simply store the bottle—ANY bottle—out of direct sunlight, such as in the glove compartment or centre console.