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Dublin: 13°C Tuesday 17 May 2022

Debunked: No, leaving hand sanitiser in your car during hot weather won’t cause it to catch fire

False claims on Facebook suggests the flammable liquid poses a threat if left in a hot car.


A POST WIDELY shared on Facebook has falsely claimed that hand sanitiser can catch fire if left in a hot car.  

The post from an Irish Facebook page says that on a warm day, a car’s interior can reach temperatures of 40 to 50 degrees Celsius in direct sunlight, which in turn could “set the bottle of sanitiser alight”.  

The post also features an image showing serious damage to the side door of a car that was allegedly caused by hand sanitiser combusting in a hot vehicle.  

Given the growth in demand for hand sanitisers during the pandemic, the ‘warning’ reads: “With temperatures creeping up, please don’t forget alcohol-based hand sanitiser is flammable.  

“Your car’s interior can reach temperatures of 40 to 50 degrees Celsius in direct sunlight and set the bottle of sanitiser alight, like in the picture. ”

The evidence 

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Firstly, the image used in the post has been widely shared both in Ireland and in other countries – including India, the US and the UK – with similar claims about leaving hand santiser in your car. 

Brazilian fact-checker Estadão first investigated the photo back in April, noting that the full image has some Portuguese writing in the background.

The picture has since done the rounds accompanying similar claims online. In the US, a Wisconsin Fire Department used the image to warn motorists against leaving hand gels in their cars.

The 21 May post was deleted from the Western Lakes Fire District of Oconomowoc Facebook page, but not before the New York Post and the Daily Mail ran stories on it, the latter warning that hand sanitiser ‘could explode’.  

Factcheckers around the world have not been able to ascertain where the image originates from. However the facts about the claim itself are clear. 

It is true that hand sanitisers are flammable, given they generally contain anywhere from 60% to 70% alcohol. But in order for a fire to start at a temperature below several hundred degrees Celsius, there would need to be a spark or source of ignition involved.  

The flashpoint of antibacterial gels – the temperature at which it gives off sufficient vapour that can be ignited by a spark or other source of ignition – is around 21 to 24 degrees Celsius. For example, the brand Carex, its antibacterial hand gels have flash points of between 22°C and 23°C.

So, while hand gels are flammable and release vapours at these flashpoint temperatures, without a spark, the flammable ingredient in hand sanitiser – ethanol - would need to be exposed to a much higher temperature than 40 to 50 degrees Celsius as claimed

For the ethanol to auto-ignite – the temperature needed for a substance to ignite without an ignition source – the inside of the car would need to reach 365 degrees Celsius,  give or take a few degrees either side. 

A recent study by Arizona State University in the US analysing cars parked in the summer heat found that temperatures mostly peaked at 71.11 degrees Celsius inside the car. So, unless you’re planning on driving into a volcano any time soon, your hand sanitiser won’t be posing any explosive threats. 

However, it should be noted that leaving sanitiser in a hot car may not the best idea as the active ingredient can evaporate and make the sanitiser less effective.

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There is a lot of false news and scaremongering being spread in Ireland at the moment about coronavirus. Here are some practical ways for you to assess whether the messages that you’re seeing – especially on WhatsApp – are true or not. 


Look at where it’s coming from. Is it someone you know? Do they have a source for the information (e.g. the HSE website) or are they just saying that the information comes from someone they know? A lot of the false news being spread right now is from people claiming that messages from ‘a friend’ of theirs. Have a look yourself – do a quick Google search and see if the information is being reported elsewhere.

Secondly, get the whole story, not just a headline. A lot of these messages have got vague information (“all the doctors at this hospital are panicking”) and don’t mention specific details. This is often – but not always a sign – that it may not be accurate.

Finally, see how you feel after reading it. A lot of these false messages are designed to make people feel panicked. They’re deliberately manipulating your feelings to make you more likely to share it. If you feel panicked after reading something, check it out and see if it really is true.

Have you gotten a message on WhatsApp or Facebook or Twitter about coronavirus that you’re not sure about and want us to check it out? Message or mail us and we’ll look into debunking it. WhatsApp: 085 221 4696 or Email: answers@thejournal.ie 

TheJournal.ie’s FactCheck is a signatory to the International Fact-Checking Network’s Code of Principles. You can read it here. For information on how FactCheck works, what the verdicts mean, and how you can take part, check out our Reader’s Guide here. You can read about the team of editors and reporters who work on the factchecks here

About the author:

Adam Daly

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