Suggest a method to liquefy atmospheric gases.

Atmospheric gases can be liquefied by applying pressure and reducing the temperature.When pressure is applied on a gas at a reduced temperature, its molecules get closer and they start attracting one another to form a liquid. When a gas is compressed by applying high pressure, a lot of heat is produced. So, while applying high pressure, it is necessary to keep the temperature low which helps to take away the heat released during compression.