In industry, compressed air is so widely used that it is often regarded as the fourth utility, after electricity, natural gas and water. However, compressed air is more expensive than the other three utilities when evaluated on a per unit energy delivered basis.
Compressed air is used for many purposes, including:
- Pneumatics, the use of pressurized gases to do work
- Vehicle propulsion (see compressed air vehicle)
- Energy storage (see compressed air energy storage)
- Air brakes, including:
- Scuba diving, for breathing and to inflate buoyancy devices
- Refrigeration using a vortex tube
- Gas dusters for cleaning electronic components that cannot be cleaned with water
- Air-start systems in engines
- Ammunition propulsion in:
Compressed Air Riser Piping from Air Compressor(s) 
The riser piping should connect to the top of the header piping and be one pipe size larger than the compressor discharge piping and/or overhead header piping. A drip leg with a drain is needed to prevent water from flowing back to the compressor. Mount valves in the highest horizontal piping (this avoids the hazard of opening a closed valve in vertical piping, and releasing trapped condensate to flow back into air compressors). All of the header main compressed air piping should slope 1/8" to 1/4" per foot down from the point of origin. Gravity and airflow will then carry condensate to the low points where drop leg should be installed to allow for removal at to accessible drop legs and drain points. These drops should be installed every 50 to 70 feet in the system and be taken from the bottom of the main line to insure as much removal as possible.
The header piping up to the air dryers is exposed to moist, hot air (temperatures can reach well over 150 degrees F). Copper, stainless steel and other piping materials that are less corrosive are recommended. If plain carbon steel piping is installed, then rust particles can pass downstream and interfere with the operation of condensate valves and wye strainers.
Compressed Air Rooms with Multiple Air Compressors 
Where multiple air compressors are to connnect the riser piping to the top of overhead piping headers. The inlet piping for Air Dryer(s) should connect to the bottom of the piping headers.
Compressed Air Distribution Piping outside of Air Compressors Rooms 
All of the header main compressed air piping should slope 1/8" per foot down from the point of origin. Gravity and airflow will then carry condensate to the low points where drop leg should be installed to allow for removal at to accessible drop legs and drain points. For larger plant, as the piping elevation lowers, a full size tee with a bottom drip leg preceding an elbow turned up to raise the pipe elevation. These drip legs & up turned elbows are typically 200 to 300 feet apart, i.e. the main piping slopes about 1/100 feet, and the elbow up raises the piping elevation 2 to 3 feet.
Compressed Air Piping Drops 
The air piping drops should connect from the top of the main piping. This prevents any condensate which forms in the main pipng from flowing into the branch pipes. Individual shut-off valves should be installed at each drop pipe to isolate it from the rest of the system for maintenance.
See also 
- Paineilma hukkaa 15 hiilivoimalan tuotannon (Finnish)
- http://isi.fraunhofer.de/isi-de/publ/download/isi04p20/compressed-air-benchmarking.pdf "Compressed Air System Audits and Benchmarking Results from the German Compressed Air Campaign "Druckluft effizient" "
- Yuan, C., Zhang, T., Rangarajan, A., Dornfeld, D., Ziemba, B., and Whitbeck, R. “A Decision-based Analysis of Compressed Air Usage Patterns in Automotive Manufacturing”, Journal of Manufacturing Systems, 25 (4), 2006, pp.293-300
- World's largest glossary of terms relating to compressed air
- A source of original articles and information related to compressed air and pneumatics
- Compressed Air and Gas Institute
- Improving Compressed Air System Performance by U.S. Department of Energy
- History of compressed air
- Compressed Air: Piping, Drying, Filtering, Regulating, Lubricating