Fans are used to transport gases under low pressures (less than 0.5 psi). Fans can be separated into two major categories: centrifugal and axial flow. Air is discharged radially from centrifugal fans and axially from axial-flow fans.


Compressors are used to increase the pressure of a fluid. The main type of compressor is the rotary compressor, meaning a rotary device is used to compress the fluid. Reciprocating and centrifugal compressors are the most common.

Aerators & Diffusers

Aerators and diffusers are used to increase the gas content of a liquid, typically oxygen in water. Diffusers are a specific type of aerator in which air is diffused through a surface and into the liquid itself. The name does not refer to the process of diffusion through the liquid.


Actuators are used to open and close valves. Pneumatic actuators use pressurized air for control. Electric actuators use electrical power (e.g. an electrical motor).