How Does an Air Compressor Work?

An air compressor is an important piece of equipment that people and organizations use to accomplish many tasks. From inflating … Continued

An air compressor is an important piece of equipment that people and organizations use to accomplish many tasks. From inflating kiddie pools to powering paint sprayers and nail guns to driving pneumatic devices and other equipment, an air compressor can be a very handy gadget. But don’t ever wonder, how does an air compressor work? Learning the basics of this equipment will help you identify the right kind of compressor for your activities.

Understanding What an Air Compressor Is

As its name implies, an air compressor is a piece of equipment or device that “compresses” or “compacts” air. It is a very simple machine that comes with three basic parts or components. They are as follows:

  • Drive

This generates power so that the other components of the device will be able to operate. There are air compressors that draw their power from a gas engine. Others have an electric motor. The latter requires electricity to run, often an electric wall outlet. In the case of more portable compressors, batteries can supply the “electricity” to the motor.

  • Pump

One can consider the pump as the heart and soul of the compressor. In a way, it is the compressor itself. Using power from the electric motor or the gasoline engine, it draws air and “compresses” it.

  • Tank

This is the storage for the compressed air. The compressed air stays here until there is a need for it.

air compressor

How an Air Compressor Works

Now that you have the answer to the question, “what is an air compressor?” it is now possible to understand how this device works. We will focus more on the piston type of air compressors because they are much more common than other systems. This type of compressor works more like the pistons in your car’s engine. The pump itself has a crankshaft, a cylinder, a piston and connecting rod, and a valve head.

Air gets sucked into the cylinder via the inlet valve located on top of the cylinder. On the opposite side of the cylinder head is another valve which releases or discharges the compressed air. Outside air will not be able to get into the cylinder without the action of the piston. Drawing its power from the electric motor or gas engine, the piston moves down the inner walls of the cylinder. This creates a vacuum in the space above it. This also lowers the pressure in this space and allows outside air through the inlet valve.

When the piston reaches the bottom of the cylinder, the upper chamber is already filled with air. Since it is already filled, the resulting air pressure closes the inlet valve so that no additional air will enter. The piston travels back to the top of the cylinder. In doing so, it compresses the air that is present within the upper part of the cylinder. Once the pressure reaches a certain pre-set limit, the discharge valve opens and the now-pressurized air gets transferred to the storage tank.

The compressor will keep on performing this cycle of piston down- and up-strokes, pushing compressed or pressurized air into the storage tank each time.

Modern compressors utilize a pressure switch which allows the system to shut off power when the storage tank pressure reaches a certain predetermined limit. For example, most single stage compressors have a preset tank pressure limit of 125 pounds per square inch (PSI). If the pressure in the tank is already at 125, then it switches off the motor.

If you use the air compressor at this time, you will be using the full 125 PSI. This also means that the air in the storage tank will also decrease as you use it. Before the tank turns empty, the pressure switch activates the motor so that the compressor can perform air compression again. It does this to maintain the correct air pressure inside the storage tank.

Unfortunately, most household applications of air compressors do not require high pressures. As such, there is a pressure regulator that can help fine-tune the amount of pressure that one needs for a particular task. The system combines two pressure gauges: one before the tank pressure regulator and another after the storage tank. The after-tank regulator keeps track of the pressure in the air line or hose. This way, you can be sure that you are using the right levels of air pressure for your tasks.

When the compressor shuts off, it will still have pressurized air in its cylinder. If it were to restart, it has to overcome the resistance of this pressurized air. To address this, the device comes with an unloader valve which conveys the pressurized air into the discharge tube. In case the pressure switch fails to turn off the air compressor, a safety valve is present to release excess pressure.

Inspecting the tire pressure

Centrifugal Type of Air Compressor

What we described above is the operation of a reciprocating type of compressor. There is another device that works in a different way. A centrifugal type of air compressor uses an impeller encased in an involute housing. Outside air enters the center of the compressor, spinning the impeller. As the impeller rotates, it increases the pressure of air while also forcing it towards the discharge outlet. The size of the area of the compressor casing decreases towards the outlet. Compression occurs as the air leaves the compressor housing.

The main advantage of such a compressor is that it does not require any pressure switch to turn the motor on and off. It provides continuous compressed air output. However, the downside is that the pressure may not be as great as that coming from a reciprocating type of compressor.

An air compressor works by drawing in air from the outside environment. It then applies pressure to this air through a variety of means, depending on the type of compressor one has. The pressurized air exits through an outlet and into a storage tank for later use. Depending on the type of compressor, the motor will keep on turning on and off to maintain the level of pressurized air in the tank.


  1. Dangers of an Air Compressor – Hunker
  2. How Does an Air Compressor Work – Campbell Hausfeld