There are several types of compressors that can be used for various applications: Piston compressors are characterized by having one or more pistons that compress the air. Piston compressors are best suited for smaller air pressure needs where they compress the air in intervals. Oil-free compressors deliver oil-free compressed air. These compressors are used in situations where oil residues can damage production quality or render products unusable. Screw compressors compress air by means of two counter-rotating screws moving in a housing. Screw compressors are used in a variety of industries.