Can Hand sanitizer auto-ignite when left in the car?

 Myth: a container of alcohol based hand sanitizer will spontaneously catch fire when exposed to sunlight.

Truth: Ethanol spontaneously catches fire at temperatures above 365 degrees Celsius and so auto-ignition in your car or house is very unlikely. However, it is advisable that clear bottles should be kept away from direct sunlight as they can cause objects around them to catch fire.

Late last year, the story of a 12 year who accidentally started a fire using a magnifying glass went viral. Apparently, the young man from Texas, USA received a magnifying glass as a Christmas present and decided to burn some old newspapers with it. Unfortunately the fire went out of control and ended burning his parents’ lawn before it was put under control. I could relate with this boy because I also went berserk the day I found out that magnifying glasses could start a fire and couldn’t wait to get my hands on one! Later, I discovered that even eyeglasses or any convex lens could be used to start a fire.

The magnifying glass concentrates the sun’s rays on to one focal point and can generate enough heat to cause dry kindling to smolder and finally catch fire.

Clear plastic or glass bottles containing any clear liquid (like water, sanitizer or drink), depending on their orientation to the sun, can also have the same effect of concentrating the sun rays to a focal point, causing a fire. It is therefore crucial that you keep bottles of water, hand sanitisers (or any clear plastic/glass bottles) away from direct sunlight whether in the car or house especially on a hot sunny day to prevent fires.

A video published by The King of random https://www.youtube.com/watch?v=QwQJ-3pZfwc gives a good illustration of the process.