The propellant used in aerosol air fresheners is normally some kind of hydrocarbon (propane/butane) and highly flammable.
The air volume inside a car isn’t that much and you only need a few % fuel to air ratio to cause an explosion. You also have to remember the air isn’t likely to be well mixed and the fuel will be localised to where the person was spraying and the lighting up.
If I remember correctly from watching myth busters I think the optimum was around 7% but you’ll get an explosion at as low as 3%. Fairly sure there was a whole episode on this topic alone.
It will only take a few PSI pressure differential over a split second of the explosion to cause that kind of damage and could be below whats needed to hurt a human.
edit: here you go
https://www.cdc.gov/niosh/docket/archive/pdfs/niosh-125/125-explosionsandrefugechambers.pdf
1 PSI over pressure will smash glass
5 PSI... will only cause the eardrums to burst in 1% of people
15 PSI... for internal injuries
35 PSI... is where you start to get fatalities.
3 PSI... will take down a house.
The air volume inside a car isn’t that much and you only need a few % fuel to air ratio to cause an explosion. You also have to remember the air isn’t likely to be well mixed and the fuel will be localised to where the person was spraying and the lighting up.
If I remember correctly from watching myth busters I think the optimum was around 7% but you’ll get an explosion at as low as 3%. Fairly sure there was a whole episode on this topic alone.
It will only take a few PSI pressure differential over a split second of the explosion to cause that kind of damage and could be below whats needed to hurt a human.
edit: here you go
https://www.cdc.gov/niosh/docket/archive/pdfs/niosh-125/125-explosionsandrefugechambers.pdf
1 PSI over pressure will smash glass
5 PSI... will only cause the eardrums to burst in 1% of people
15 PSI... for internal injuries
35 PSI... is where you start to get fatalities.
3 PSI... will take down a house.
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