Why Does Compressed Air Get Cold?

If you’ve ever used compressed air or cans of compressed air, then you know that they can get very cold.

Why does compressed air get cold?

Canned “compressed air” gets cold because of evaporation and expansion. The can holds a gas that is mostly compressed into a liquid, not air. When you spray it, the pressure in the can drops, some of the liquid boils into gas, and that takes heat out of the can.

In this article, you’ll learn everything you need to know about, “Why does compressed air get cold?”

Why Does Compressed Air Get Cold? (The Science)

So why does compressed air get cold when released?

Compressed air gets cold because the liquid in the can evaporates and the gas expands as it leaves the nozzle.

Adiabatic Expansion

Adiabatic expansion is a process in which a gas expands without exchanging heat with its surroundings.

The word “adiabatic” comes from the Greek prefix “a,” meaning “not,” and the word “dia,” meaning “through.” 

Together, these prefixes indicate that no heat is exchanged during adiabatic expansion. 

Instead, the temperature drops because the gas does work as it expands, which uses up some of its internal energy.

The reverse also holds. When a gas is compressed without losing heat, work is done on it and its temperature rises, which is why a bicycle pump gets warm.

Thermodynamics

When you compress air, you are increasing the air’s pressure. 

When the pressure is released, the gas expands and does work pushing against the air around it. That work comes out of its own internal energy, so it cools down.

In a can of duster, the bigger effect is the liquid inside boiling off as you spray, which draws heat from the can. That is why the can feels cold in your hand.

Compressed air also has a higher density than regular air. This means that there are more molecules in a given volume of compressed air than there are in the same volume of regular air. 

Why Does Compressed Air Get Cold Upside Down?

Compressed air gets cold upside down because of the contents of the canned air.

Also, because of physics.

Canned air is not actually air. The can holds a gas, commonly difluoroethane, that is mostly compressed into a liquid.

Flipping the can upside down changes what comes out. Upside down, liquid shoots out, not gas.

Why? When the bottle is standing upright, a gas layer rests at the top of the can near the nozzle.

But, upside down, that gas isn’t there to prevent the liquid from spraying out.

Upside down, the gas is no longer at the “top” near the release nozzle.

As the liquid leaves the can, it boils almost instantly and cools rapidly.

The molecules move further apart and take up more space, which requires more energy. 

This energy comes from the liquid itself and whatever it touches, which is why the spray can chill skin quickly and deeply. Keep the can upright when you spray, and never spray the liquid on yourself or anyone else.

Use canned air in a ventilated space and never inhale it on purpose. Washington State’s workplace safety agency warns that the gas can displace air in enclosed areas and cause oxygen deficiency.

Why Does Compressed Air Get Cold When Released?

The release of compressed air triggers the state change from liquid to gas and lowers the pressure of the air as it expands and evaporates. 

The “release” is the trigger for the temperature change and that’s why compressed air gets cold when released. 

As the air expands, it cools down. 

Why Do Aerosols Get Cold?

Another way to ask this question is, “Why does canned air get cold?”

Aerosols are great for dusting off electronics, but have you ever noticed that they feel cold when you use them? 

It turns out that there’s a scientific reason for this.

Aerosol cans actually contain a liquid. This liquid rapidly evaporates when the pressure is reduced slightly – that way, a large amount of gas can be stored in a small, low-pressure can.

When you press the nozzle on an aerosol can, this releases vapor, lowering the internal pressure and allowing the liquid to evaporate. 

As the liquid evaporates, it cools down – and that’s why aerosols feel cold when you use them.

Here is a good video about why compressed air cans get cold:

Does Compressed Air Get Hot or Cold?

Compressed air gets hot.

To understand how compressed air gets hot, it’s important to first understand what happens to air when it’s compressed. 

When air is compressed, the molecules are pushed closer together. 

Compressing the air does work on it, which raises its temperature. The more air that is compressed into a smaller space, the hotter it will become.

However, when compressed air is released, the molecules expand and cool down. 

This is why decompressed air feels cooler than the surrounding air.

Does Compressed Air Get Cold Because of a Chemical Reaction?

You might have heard that compressed air gets cold because of a chemical reaction. 

But is this really true? The short answer is no. Not really. 

The real reason is physical, not chemical.

Here’s a closer look at how it works.

When you compress air, you are essentially increasing the number of molecules in a given space. 

Compressing a gas does work on it and raises its temperature. The gas cools only when it later expands and does work on its surroundings, which lowers the average kinetic energy of its molecules.

This decrease in temperature is due to the loss of kinetic energy, not to any sort of chemical reaction.

Final Thoughts: Why Is Compressed Air Cold?

The bottom line is that canned air gets cold because the liquid inside evaporates and the gas expands when you spray it.

Thanks for reading!

Feel free to browse around this site for many other articles about cold-related topics.

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Sources

National Center for Biotechnology Information
Research Gate

Reviewed October 2026. We corrected the physics explanations and added safety advice, using OpenStax University Physics and Washington State workplace safety guidance.