Air compressor selection

When purchasing an air compressor there are several things to consider

How much ACFM (actual cubic feet per minute) "free air" do I need? ACFM is often confused with pressure PSI. Many people think as long as the compressor will build let's say 100 PSI that will be fine. You can build 100 PSI with a bicycle pump but it wont operate air tools or plant equipment. Therefore you need to know the total ACFM for all of your equipment. Lets say you have a body shop and your grinders, files and sanders consume 15 ASCM @ 90 PSIG if they were all operating at once. You would need an air compressor that would produce a minimum of 15 ACFM to operate everything. But lets go one step further. Unless you are willing to purchase a rotary screw air compressor that has a duty cycle of 100%, you would need to oversize a reciprocating compressor by a minimum of 30%. That means you would need a compressor that produces a minimum of 19 ACFM "free air" to operate your equipment and give the air compressor a rest. Many people guess at things, buy a compressor that has an attractive price and when it burns up from over duty cycle( they really don't know what caused it) then they are dismayed. Of course most equipment is not operating all at the same time but its better to over calculate some than to wear out the compressor.