Air compressors are one of the most vital pieces of equipment in your woodshop. They are used for various reasons, such as running air tools or cleaning equipment, so size does matter.
Big shops that routinely use air-heavy tools most likely will need to invest in a stationary compressor, such as a rotary screw compressor. These compressors push out air at a higher PSI and can handle more than two tools being used at the same time. For example, a spray gun or sander that require a higher psi would be used with a stationary compressor.
Smaller shops will most likely need a portable compressor, such as a Garage Mate, Twin-Stack or portable wheelbarrow compressor. If you are running a nail or framing gun, those can operate on the air supplied by a smaller portable machine.