Is Leaving Hand Sanitiser in Your Car Dangerous?

As lockdown restrictions ease across the UK and the weather becomes warmer, the advice is to stay alert and continue cleaning our hands to stem the spread of the coronavirus. Many of us, including every single Beta Group engineer, now carry a small bottle of hand sanitiser in our cars and bags.

Having seen reports hand sanitiser bottles explode in cars that are left in high temperatures, Beta Group decided to carry out its own research.

How Hot Does a Car Get in the Sun?

In a study conducted by Arizona State University and the University of California at San Diego School of Medicine researchers found that the cabin of a car parked in the sun on a hot summers day for an hour would reach a temperate of 116°F (approx. 47°C). The same study found that a car parked in the shade for the same amount of time would reach a cabin temperature of 100°F (approx. 38°F).[1]

How Does a Fire Start?

Every fire needs fuel, air, and heat. There must be fuel to burn, air to supply oxygen, and heat to start and continue the combustion process. In a parked car scenario, the fuel is the alcohol in the hand sanitiser, the air is the oxygen around us, and the heat is from the sun. The one thing missing is the spark.

For items described by the HSE as being flammable, liquids which have a flashpoint equal to or greater than 21°C, hand gel can release vapour that is flammable, but for the car to catch fire, an external source of ignition is required.[2][3]

What about Auto-Ignition?

The main ingredient in hand sanitiser is alcohol, also known as the chemical compound Ethanol. Ethanol has an auto-ignition point of 365°C; stratospherically higher than the temperatures a car would reach if left out in the sun for an hour.[4]

The Impact on Effectiveness

During our research, we found leaving hand sanitisers in the sun for an extending period of time has an impact on the effectiveness of the product when being used to clean hands.

Alcohol is a liquid; heat causes liquids to evaporate. The longer you leave the hand gel in your car in the heat, and the more often you do so, over time, the percentage of ethanol in the hand sanitiser will reduce and the hand gel will become less effective at killing germs.

The best advice we can give is to always carry hand sanitisers in a bag or a purse or in a pocket and carry it around with you. Throughout the day we’re subconsciously touching objects left, right and centre, and who knows who’ll have touched them before us or who will touch them afterwards. All we can do is ensure we are doing our best to stop the spread of COIVD-19.

Hand Sanitisers will not Stop the Spread

Simply cleaning your hands for twenty seconds with soap and water and using hand sanitiser after touching objects will not stop the spread of COVID-19. If you’re working in an office, you must be adhering to social distancing rules. If you’re on the road and completing projects in commercial properties, face masks and PPE should be worn.

Practice Caution. Do Not Take Risks

The evidence suggests the reports of hand sanitisers exploding inside cars may have been fabricated, and hand sanitisers may not catch fire if left out in the sun; however, the reason we use hand sanitisers is to keep our hands germ free, so even if they don’t explode, they may lose their effectiveness.

Take your hand sanitiser with you and keep it on your person. Use it regularly. Keep your hands clean. Help reduce the spread of the coronavirus by wearing PPE and using hand sanitiser gels as often as possible.


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