Air Compressor Terminology/Technical Terms You Should Know

Having an air compressor around the house can make tasks more time efficient. For example, you could use it to power nail guns, provide compressed air for tires, or to whip up a batch of whipped cream. Here are some technical terms that will help you figure out how to operate your new unit.

The motor is what provides power to the whole system and works by rotating an output shaft on which pulleys are mounted so they spin freely.

Here you can obtain a list of commonly used air compressor terms and phrases. If you read reviews on air compressors, you will see these words very often.

Cylinder and Piston

Cylinder is a hollow space inside a pump in which a piston travels upward and downward. You must have seen a medical syringe, in which the black rubber connected on the top of a plunger is called seal. This seal is almost similar to the piston and the barrel in which the seal and plunger move backward and forward is similar to a cylinder. I hope this example helped you a lot.

Read more: Air compressor maintenance

Drain Valve

You will see a valve under the tank that is given to drain water from the tank. Air includes moisture that goes into the tank with air. With time, moisture gets condensed and forms into water. That is why you see water coming out from the tank when the valve is opened.

To prolong the lasting of any air tank, users should drain water at the end of the day to let the tank dry. Otherwise the tank will get rust and damage very shortly.

Duty Cycle

Duty cycle is a measure of how much time an air compressor is actually performing the work of compressing air, and not idle. The work hours are subtracted from the total hours used by the compressor, and this percentage is called the duty cycle.

In general, an air compressor's duty cycle should be at least 20% to 25%.  A 50 % duty cycle compressor can run 30 minutes of an hour. Then you should give the unit rest for 30 minutes. 100% duty cycle compressor can run endlessly.

Decibel (dBA)

Many of you have heard of decibel; this is related with the measurement of sound. In case of air compressor, the word decibel is used to inspect the noise level of the motor a compressor has. For home use compressor, 82 dBA (or less) is regarded to be standard.  Commercial use compressors are noisy and hardly be found below 70 dBA.


Air Compressor needs a tank to store pressurized air. The tank can be of different sizes. Whereas many containers are calculated in liter, air compressor tank is considered as gallon. A 1-gallon tank is smaller than a 2-gallon tank.

Gauges & Regulator

All the compressors include two pressure gauges for visual monitoring. One gauge is included to check tank pressure (PSI) and the other one is to fix out put pressure (CFM) that you want to supply for your air tools. To clarify, you have a blower that needs 2.0 CFM @ 90 PSI. You can produce this rating checking the PSI gauge and CFM gauge.

Whereas CFM gauge is to watch the rating you are delivering, regulator is to fix the air flow rating visible in the cfm gauge.


The term "horsepower" is typically used in reference to the unit of measurement that measures power on a machine or engine. The horsepower rating for an air compressor can be found by multiplying its cubic feet per minute output with 1/7th.

For example: A 100 CFM air compressor has a 7 HP rating. However, this definition does not take into account other factors which may affect the actual performance of the equipment. 

The bigger is the number, the power the motor has. To know the exact power of a compressor, follow the running horsepower (RHP). Some manufacturing companies display the pick HP for marketing and show the RHP in small font. Don’t fool yourself with the pick HP.

What Is PSI and CFM

PSI stands for Pound Per Square Inch. This is the unit to measure tank pressure of an air compressor. You have noticed of an air compressor that can store pressure inside the tank at 100 PSI or 150 PSI.

Between two 5 gallon air tanks, the tank with 150 PSI will have more air storage compared to the tank having 100 PSI rating.  When a great volume of air compressor is stored in a tank, the pressure increases and that pressured is measured by the unit PSI.

As with all the pneumatic tools, you will find this term as a requirement pressure. If the pressure exceeds the required pressure for a particular air tools, you are going to spoil it right away. That is why when you are running an air tools, check the user guide so that you can set the right pressure for the tools.

CFM stands for Cubic-Feet Per Minute; a measuring unit for air flow comes out from the air tank.  All air compressor has regulator to control air flow comes out from the exhaust coupler and there is a gauge as well to check the desired rating is delivered accurately.

All air compressors come with a fixed CFM rating and you cannot increase the CFM. So, new buyers should be careful what CFM they do need when purchasing a compressor.

Horizontal VS Vertical Tank

Air compressor tanks can be of diverse shapes. Vertical tank is placed in vertical position and horizontal tank is positioned in parallel. Usually horizontal tanks are located on massive stationary compressors. Medium sized compressors under 100-gallon are found to be vertically placed tank. Vertical tank has small foot print which is a buying factor to many customers.


Pump is the fundamental section for an air compressor which compresses air under pressure and delivers to the tank. Two types of pumps are available for air compressor: Single Stage Pump and Two Stage Pump

There are at least two pumps in a two-stage air compressor. Two-stage pump is more powerful than one-stage pump that can build pressure from 145 to 175 PSI. It compresses air in two steps; larger low-pressure cylinder supplies air to a smaller high-pressure cylinder and then the small cylinder delivers air to the cylinder under high pressure.

Safety Valve

An air compressor’s safety valve is a pressure release that is attached to the discharge hose of an air compressor. If the pressure inside the tank becomes too high, then the safety valve will release any excess pressure before it damages the equipment.

Safety valves also allow for a controlled rate of flow of compressed air to be released from the tank without compromising the quality or pressure of gas being discharged from the outlet.

To clarify, the compressor motor shuts by itself when the PSI or air storage reaches to its limit. For technical faults if the motor run continuously, the safety valve releases excess air pressure thus ensures secured job environment.

A safety valve not only saves the device from explosion or damage but also saves your life. Given that it is indispensable to check the valve sometimes to make sure the proper functionality. Clean it if found to be covered by excessive dust.


Air compressor needs storage to hold air pressure coming from the compressor pump. This storage is called Tank or Receiver. A tank is very essential for not only storage but also for required pressure that should be supplied to power pneumatic tools.

Air compressor can be of different built materials like aluminum, cast iron, and steel. Big compressors used in industries and repairing shop are generally cast iron built to make it strong and long lasting. cast Iron built air compressor tank requires maintenance to avoid rust.

There are some small compressors that are frequently bought for home uses. The tanks of these compressors are sometimes constructed with aluminum or steel to make it light so that users can feel comfortable to carry here and there.

In conclusion, there are many air compressor technical terms that you should be aware of. By being familiar with these terms, you will be able to better understand your air compressor and its function. If you are ever unsure about a term, be sure to consult your air compressor's manual or contact the manufacturer for more information.

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