How does air conditioning work?

Inside the unit, a liquid refrigerant flows through a cold coil called the evaporator, where it absorbs heat from indoor air blown across it and turns into a gas. A compressor then squeezes the gas, raising its pressure and temperature. The hot gas travels to the outdoor condenser coil, where a fan helps it release heat into the outside air and turn back into a liquid. An expansion valve then drops the pressure, making the refrigerant very cold again, and the cycle repeats. Air conditioners also dry the air, because moisture condenses on the cold coil and drains away.