– How do propellants work with aerosol sprays?

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Could someone please explain this in a simple way?

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Today’s aerosol cans typically use Propane, Butane, Isobutane or Dimethyl Ether as propellants. CFCs were famously used decades ago and were banned due to the damage they were doing to the Ozone layer.

These gases have a very low boiling point, Propane for example boils at -42 C. This means that they boil instantly at room temperature, so if liquid propane is put onto a table at room temperature it will boil and become a gas.

So to store them as a liquid you have to do so under pressure, like in an aerosol can.

This pressure is what squeezing the material (like paint) out of the can when you open the nozzle.

The Propane becomes a gas almost instantly atomizing the compounds which in turn gives you that even spray.

The downside is that propane and the other compounds are highly flammable. But stay in the area for only a few seconds before dispersing. Therefore so long as you aren’t spraying near and open flame, the risk is low.

Other safer gases like CO2 for example has the downside that it doesn’t become a liquid under pressure, it becomes a solid (dry ice). While Nitrogen doesn’t become a liquid at aerosol can pressures, it remains a gas so it can’t produce the pressures required. Similarly with Oxygen, but Liquid Oxygen is also extremely dangerous.