Compressor Buyers Guide

The Sealey Guide to Compressors

Choosing the right Compressor

Sealey offer an extensive range of compressors. This guide is designed to help you make the right choice for your needs.


The cfm rating of each air tool defines the amount of air required to power the tool in cubic feet per minute. Determine the highest cfm rating of the air tools you intend to use. If you intend using more than one tool at the same time, you will need to add the ratings of both tools to calculate the total cfm rating. A 50% safety margin then needs to be added e.g. a 4cfm tool would require a 6cfm output compressor. Now you can look for the compressor that produces a high enough cfm output for your needs. When comparing models, ensure that you are reviewing the Free Air Delivery and not Air Displacement.


The compressor’s horsepower, typically rated between 1.5 and 7.5, measures the amount of work an engine can perform. The higher the horsepower, the quicker the air is replaced in the air tank. This will allow less downtime between each job. It also allows the motor to work for shorter periods of time.

Tank Size

The size of the tank will determine how long you can use your air tools before needing to let the tank fill up again. A longer job, such as sanding will require a larger compressor. Using a 4cfm sander will require a compressor with a minimum Free Air Delivery of 6cfm. An air tool requiring a higher air output will drain the tank quicker, so the size you need depends on the job at hand and how long the task will take.

Amount of Usage

Compressors need to cool down between regeneration periods. Regeneration is when the pump replaces the air that has been used from the compressor’s air tank.

Electric or Petrol Driven

If you plan to use the compressor where there’s no electrical supply, you will need to opt for a petrol version. If choosing electric, ensure your power supply is adequate to run the compressor. Some larger compressors cannot be run from a 13A socket.


Belt driven machines are quieter than direct drive versions, but some compressors have noise suppressing casings to reduce noise pollution. Low noise compressors allow use indoors and enable closer proximity to the unit.

Oil lubricated or oil-free

Oil-free compressors need less maintenance and have lower running costs than models which require oil to operate. An oil-free compressor is also essential for applications where oil contaminants are prohibited. An oil lubricated compressor can have a longer life, due to less friction and wear within the unit, and is suitable for running standard air tools.

Air accessories

Air hoses or reels will help the delivery of air to your tools. Different airline couplings may be required to allow the maximum potential from your air tools and to permit the use of multiple air lines from your compressor. To deliver consistent pressure to an air tool or water trap, a regulator should be fitted in the airline. A lubricator or air filter may be worth investing in, depending on the application. Although, you must ensure that all accessories match the specifications of the compressor being purchased.

View our current range of Compressors here: