Air Compressor Glossary & Terms

Here are a few terms related to air compressors and a definition for each, a mini dictionary, air compressor vocabulary.


Designed to reduce the temperature and liquefy condensate vapors.
Air Dryer
A device that is generally associated with larger air compressor systems that helps with the removal of water from the tank and line.
Check Valve
A device that allows fluid or air to flow in only one direction.
Coalescing filter
A specific type of filter that not only works to remove dust and particles from the air, but also oil from the air lines.
Cubic Feet Per Minute (CFM)
The volume of air that is able to pass through an opening in one minute.
A material used with air compressors and air dryers that helps to remove water vapor from the air.
Drain Cock
Used to release accumulated moisture from the compressor tank (Also see drain valve).
Drain Valve
A drain valve works to remove surplus liquid from the compressor. There are manual, float and electronic types of drain valves.
Compressor tanks are made of steel, when water gets into the tank, the tank can rust thus reducing the life of the compressor. A dryer dries the air in the tank, reducing the amount of water collected.
Dual Stage
Compressors where air is compressed from initial pressure to an intermediate pressure in one or more cylinders.
Duty Cycle
Amount of time that a compressor can operate at full load over a thirty minute time  period.
Filter Efficiency
The rate of which a filter can remove particles from an air flow.
Filter housing
Cover which protects the filter assembly.
Kick-in Pressure
Factory set low pressure point of the pressure switch that starts the compressor to re-pressurize the tank to a higher pressure.
Kick-out Pressure
Factory set high pressure point of the pressure switch that stops the compressor from increasing the pressure in the tank above a certain level.
Load Time
The time it takes for a compressor to go from load to unload.
Low oil shutoff
A feature which shuts off the engine if it runs low on oil, preventing damage or failure.
Oil free compressor
Air compressor that has no oil inserted into the compression chamber for lubrication, cooling or sealing. Typically used in the medical and food processing field.
Related to the movement of air.
Pneumatic power
Compressed air power.
Point of use
An outlet in a building used to connect tools or equipment to the air compressor system.
Pounds Per Square Inch (PSI)
A unit of measurement referring to the pressure applied on one square inch of an object's surface.
Pressure Switch
An instrument which senses a change in pressure and automatically adds or decreases air in the tank.
Preventative Maintenance (PM)
A maintenance program performed on a fixed schedule that includes compressor service as well as routine repair and replacement of parts.
The elimination of undesired gas or liquid from a system.
Generally a tank used for storage of compressed air. Often times in large air compressor systems there can be a primary and secondary receiver.
Reciprocating Compressor
A reciprocating compressor uses pistons driven by a crankshaft to deliver air at high pressure.
Rotary Screw Compressor
A compressor which utilizes two intermeshing helical rotors to trap a volume of air, then compress it to a higher pressure. Rotary screw compressors can be run at lower temperatures for 24 hours per day, 365 days a year.
Safety valve
A valve which limits fluid pressure by releasing some of the pressurized liquid or gas. a.k.a. Pressure Relief Valve.
Single Stage
A compressor in which the air is compressed from initial pressure to final pressure in one step.
A valve that is between the compressor pump and tank. It opens when the compressor stops, that "psssssst" sound. This enables the compressor to start easier the next time.
Vacuum Pumps
A vacuum pump is a compressor that operates with an intake pressure below atmospheric and discharge pressure.