Editing Compressed air

{{Short description|Air under a pressure greater than atmospheric}}
{{About|air under pressure|canisters inaccurately marketed as "compressed air"|gas duster}}
[[File:Single_Stage_Portable_Air_Compressor.jpg|thumb|upright=1.2|Technical Illustration of portable single-stage air compressor]]
'''Compressed air''' is [[air]] kept under a [[pressure]] that is greater than [[atmospheric pressure]].  Compressed air in vehicle [[tire]]s and [[shock absorber]]s are commonly used for improved traction and reduced vibration. Compressed air is an important medium for the transfer of energy in industrial processes and is used for [[power tool]]s such as [[air hammer (fabrication)|air hammer]]s, [[Jackhammer|drills]], [[power wrench|wrench]]es, and others, as well as to atomize paint, to operate air cylinders for automation, and can also be used to propel vehicles. Brakes applied by compressed air made large railway trains safer and more efficient to operate. Compressed air brakes are also found on large highway vehicles.

Compressed air is used as a breathing gas by [[underwater diving|underwater diver]]s. The diver may carry it in a high-pressure [[diving cylinder]], or [[surface supplied diving|supplied from the surface]] at lower pressure through an [[air line]] or [[diver's umbilical]].<ref name="US Navy Diving Manual 2016">{{cite book|last=US Navy|title=U.S. Navy Diving Manual Revision 7 SS521-AG-PRO-010 0910-LP-115-1921|url=https://www.navsea.navy.mil/Portals/103/Documents/SUPSALV/Diving/US%20DIVING%20MANUAL_REV7.pdf?ver=2016-12-14-135043-757|date=1 December 2016|publisher=US Naval Sea Systems Command|location=Washington, DC.|ref={{harvid|US Navy Diving Manual|2016}}|url-status=live|archive-url=https://web.archive.org/web/20161228033101/http://www.navsea.navy.mil/Portals/103/Documents/SUPSALV/Diving/US%20DIVING%20MANUAL_REV7.pdf?ver=2016-12-14-135043-757|archive-date=28 December 2016}}</ref> Similar arrangements are used in breathing apparatus used by firefighters, mine rescue workers and industrial workers in hazardous atmospheres.

In Europe, 10 percent of all industrial electricity consumption is to produce compressed air—amounting to 80 [[terawatt hour]]s consumption per year.<ref name="tekniikkatalous">{{cite web |url=http://www.tekniikkatalous.fi/energia/article218734.ece?s=u&wtm=tt-24022009 |title=Paineilma hukkaa 15 hiilivoimalan tuotannon |first=Raili |last=Leino |date=24 February 2009 |language=fi |url-status=dead |archive-url=https://web.archive.org/web/20110717044303/http://www.tekniikkatalous.fi/energia/article218734.ece?s=u&wtm=tt-24022009 |archive-date=17 July 2011 |access-date=24 February 2009 }}</ref><ref name="fraunhofer">{{Cite web |url= http://isi.fraunhofer.de/isi-de/publ/download/isi04p20/compressed-air-benchmarking.pdf |archive-url= https://web.archive.org/web/20111224105715/http://isi.fraunhofer.de/isi-de/publ/download/isi04p20/compressed-air-benchmarking.pdf |url-status= dead |archive-date= 2011-12-24 |title=Compressed Air System Audits and Benchmarking Results from the German Compressed Air Campaign "Druckluft effizient"}}</ref>

Industrial use of piped compressed air for power transmission was developed in the mid-19th century; unlike [[steam]], compressed air could be piped for long distances without losing pressure due to condensation. An early major application of compressed air was in the drilling of the [[Mont Cenis Tunnel]] in Italy and France in 1861, where a 600 kPa (87 psi) compressed air plant provided power to [[Jackhammer|pneumatic drills]], increasing productivity greatly over previous manual drilling methods. Compressed-air drills were applied at mines in the United States in the 1870s. [[George Westinghouse]] invented [[Railway air brake|air brakes]] for trains starting in 1869; these brakes considerably improved the safety of rail operations.<ref>Lance Day, Ian McNeil (ed.), ''Biographical Dictionary of the History of Technology'', Routledge, 2002, {{ISBN|1134650205}}, p. 1294</ref> In the 19th century, Paris had a system of pipes installed for municipal distribution of compressed air to power machines and to operate generators for lighting. Early air compressors were steam-driven, but in certain locations a [[trompe]] could directly obtain compressed air from the force of falling water.<ref>Peter Darling (ed.), ''SME Mining Engineering Handbook, Third Edition'' Society for Mining, Metallurgy, and Exploration (U.S.) 2011, {{ISBN|0873352645}}, p. 705</ref>

==Breathing==
[[File:Diving cylinders.jpg|thumb|upright|[[Diving cylinder]]s used to store compressed air or other breathing gasses for underwater diving]]
Air for breathing may be stored at high pressure and gradually released when needed, as in [[scuba diving]] and self-contained breathing apparatus [[SCBA|(SCBA)]] or used by firefighters and industrial workers, or produced continuously to meet requirements, as in [[surface-supplied diving]]. Air for breathing must be free of oil and other contaminants; carbon monoxide, for example, in trace volumetric fractions that might not be dangerous at normal atmospheric pressure may have deadly effects when breathing pressurized air due to proportionally higher [[partial pressure]]. Air compressors, filters, and supply systems intended for breathing air are not generally also used for pneumatic tools or other purposes, as air quality requirements differ.<ref name="USNDM R6" >{{cite book |author=U.S. Navy Supervisor of Diving |title=U.S. Navy Diving Manual |version=SS521-AG-PRO-010, revision 6 |year=2008 |publisher=U.S. Naval Sea Systems Command |url=http://www.supsalv.org/pdf/Dive%20Manual%20Rev%206%20with%20Chg%20A.pdf |access-date=2014-01-21 |ref={{sfnref|U.S. Navy Diving Manual|2008}} |url-status=dead |archive-url=https://web.archive.org/web/20141210095431/http://www.supsalv.org/pdf/Dive%20Manual%20Rev%206%20with%20Chg%20A.pdf |archive-date=2014-12-10 }}</ref>

Workers constructing the foundations of bridges or other structures may be working in a pressurized enclosure called a [[Caisson (engineering)|caisson]], where water is prevented from entering the open bottom of the enclosure by filling it with air under pressure. It was known as early as the 17th century that workers in [[diving bell]]s experienced shortness of breath and risked asphyxia, relieved by the release of fresh air into the bell. Such workers also experienced pain and other symptoms when returning to the surface, as the pressure was relieved.  [[Denis Papin]] suggested in 1691 that the working time in a diving bell could be extended if fresh air from the surface was continually forced under pressure into the bell. By the 19th century, caissons were regularly used in civil construction, but workers experienced serious, sometimes fatal, symptoms on returning to the surface, a syndrome called caisson disease or [[decompression sickness]]. Many workers were killed by the disease on projects such as the [[Brooklyn Bridge]] and the [[Eads Bridge]] and it was not until the 1890s that it was understood that workers had to decompress slowly, to prevent the formation of dangerous bubbles in tissues.<ref>E. Hugh Snell, ''Compressed Air Illness Or So-called Caisson Disease'' [[H. K. Lewis & Co. Ltd.|H. K. Lewis]], 1896 pp.</ref>

Air under moderately high pressure, such as is used when diving below about {{convert|20|m|ft|-1}}, has an increasing [[narcotic]] effect on the nervous system. [[Nitrogen narcosis]] is a hazard when diving. For diving much beyond {{convert|30|m|ft|-1}}, it is less safe to use air alone and [[Breathing gas|special breathing mixes]] containing helium are often used.<ref name="Bennett and Elliott 2003" >{{cite book |last1=Bennett |first1=Peter |last2=Rostain |first2=Jean Claude |title=Bennett and Elliott's physiology and medicine of diving |edition=5th |editor1-last=Brubakk |editor1-first=Alf O |editor2-last=Neuman |editor2-first=Tom S |year=2003 |publisher=Saunders |location=United States |chapter=Inert Gas Narcosis |isbn=0-7020-2571-2 |oclc=51607923 }}</ref>

In land-based applications, [[SCBA]]s, UEBSS (USA), and EBBS (EU) provide breathable air for emergency responders, industrial workers, and military personnel in hazardous environments. These devices use compressed air cylinders to supply clean air to the wearer, ensuring safety in oxygen-deficient or contaminated atmospheres. To enhance operational safety and efficiency, Kee Connections Buddy Breather coupling<ref>{{Cite web |date=2023-04-03 |title=EBSS Range for SCBA - Patented Solutions by Kee Connections |url=https://www.keeconnections.co.uk/ebss-range/ |access-date=2025-02-20 |language=en-GB}}</ref> allows users to share air in emergency situations. This coupling system enables firefighters or other SCBA users to connect their breathing apparatuses, providing life-saving air support when needed. Such innovations help improve survivability and teamwork in high-risk conditions.

==Uses==
[[File:Kompressorstation mit Druckluftspeicher.jpg|thumb|upright|Air compressor station in a power plant]]
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.<ref>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</ref>
[[File:Two-stage_air_compressor_assembled_on_a_horizontal_tank_and_equipped_with_a_Joule-Thompson_(JT)_type_refrigerated_compressed_air_dryer.jpg|thumb|Two-stage air compressor assembled on a horizontal tank and equipped with a Joule-Thomson (JT) type refrigerated compressed air dryer]]

Compressed air is used for many purposes, including:
* [[Pneumatics]], the use of pressurized gases to do work
** [[Pneumatic tube#Pneumatic post|Pneumatic post]], using capsules to move paper and small goods through tubes.
** [[Air tool]]s
** [[HVAC control system]]s
** [[Spray painting]] 
* Vehicle propulsion (''see'' [[compressed-air vehicle]])
* [[Energy storage]] (''see'' [[compressed-air energy storage]])
* Recreation – Amusement Parks, Golf Courses (Sprinkler Systems), Hotel elevators, Ski Resorts (Snow making)
* Air brakes, including:
** [[Air brake (rail)|Railway braking systems]]
** [[Air brake (road vehicle)|Road vehicle braking systems]]
* [[Underwater diving]], [[breathing gas|for breathing]], to inflate [[Buoyancy compensator (diving)|buoyancy compensator devices]] and [[lifting bag]]s, and for [[airlift dredging]] 
* [[Refrigeration]] using a [[vortex tube]]
* [[Air-start system]]s in engines
* Ammunition propulsion in:
** [[Air gun]]s
** [[Airsoft]] equipment
** [[Paintball]] equipment
* Cleaning dust and small debris in tiny spaces
* [[Abrasive blasting]] for removing corrosion products and coatings
* [[Injection molding]]
* [[Airbrush]]ing used by [[Rail transport modelling|model railroaders]] and other hobbyists to paint and weather cars, boats, planes and trains
* Food and beverage capping and [[fermentation]]<ref>{{Cite web|url=http://www.cagi.org/working-with-compressed-air/applications.aspx|title=Applications - Working With Compressed Air - CAGI - Compressed Air And Gas Institute|website=www.cagi.org|access-date=2017-01-12|url-status=live|archive-url=https://web.archive.org/web/20170128110742/http://www.cagi.org/working-with-compressed-air/applications.aspx|archive-date=2017-01-28}}</ref>
* Compressed air from Lysefjorden/[[Preikestolen]] (Norway) is being sold in cans, mostly to China.<ref>{{cite news |url=http://www.aftenbladet.no/nyheter/okonomi/Selger-frisk-luft-fra-Preikestolen-pa-eBay-3976326.html?spid_rel=2 |title=Selger frisk luft fra Preikestolen på eBay |work=[[Stavanger Aftenblad]] |language=no |access-date=15 August 2016 |url-status=live |archive-url=https://web.archive.org/web/20160818080123/http://www.aftenbladet.no/nyheter/okonomi/Selger-frisk-luft-fra-Preikestolen-pa-eBay-3976326.html?spid_rel=2 |archive-date=18 August 2016 }}</ref>

=== Emergency services and firefighting ===

* Self-Contained Breathing Apparatus ([[Self-contained breathing apparatus|SCBA]]) – Used by firefighters, rescue workers, and hazmat teams for breathing in hazardous environments.
* [[Fire suppression system|Fire Suppression Systems]] – Some fire suppression systems, such as dry chemical and CO₂ systems, use compressed air to discharge fire-extinguishing agents.
* Rescue Tools (Pneumatic [[Hydraulic rescue tool|Jaws of Life]]) – Hydraulic or pneumatic-powered rescue tools used to cut through vehicles and debris during emergency extrications.
* Inflatable Rescue Devices – Air-powered inflatable boats, flotation devices, and emergency life rafts.

=== Medical  ===

* [[Ventilator]]s and [[Respirator]]s – Compressed air is used in hospitals and ambulances to power ventilators and oxygen delivery systems.
* [[Dental instrument|Dental Equipment]] – Dentists use compressed air to power drills and cleaning tools
* [[Hyperbaric chamber]]s – Used for treating decompression sickness, wound healing, and other medical conditions requiring high-pressure oxygen therapy.
* [[Oxygen mask|Portable Oxygen Systems]] – Some emergency and home healthcare oxygen systems use compressed air for efficient delivery.

== Energy Costs of a Compressed Air System ==
Regarding operating costs, it is important to consider that compressed air represents a significant portion of total energy costs. Roughly, every 1 kW of power produced requires 8 kW of electrical power.<ref>{{Cite web |title=Compressed Air – Simple Guide to size a compressor part 1 |url=https://www.chemengconsulting.com/blog/2025/02/03/compressed-air-simple-guide/940/}}</ref>
Additionally, considering the lifecycle of a compressed air system (about 10–15 years), the total costs can be broken down as follows:

* 70–75%: Energy costs
* 15–20%: Compressor, accessories, piping, and installation costs
* 10%: Maintenance costs

==Design of systems==
Compressor rooms must be designed with ventilation systems to remove [[waste heat]] produced by the compressors.<ref>{{Cite news |url=https://kaesertalksshop.com/2015/05/05/some-like-it-hot-your-compressor-room-doesnt/ |title=Some Like It Hot…Your Compressor Room Doesn't |date=5 May 2015 |newspaper=Kaeser Talks Shop - Compressed Air Tips from the Experts at Kaeser Compressors |access-date=2017-01-12 |url-status=live |archive-url=https://web.archive.org/web/20170113165807/https://kaesertalksshop.com/2015/05/05/some-like-it-hot-your-compressor-room-doesnt/ |archive-date=13 January 2017 }}</ref>

===Water and oil vapor removal===
{{See also|Compressed air filters}}
When air at atmospheric pressure is compressed, it contains much more water vapor than the high-pressure air can hold. [[Relative humidity]] is governed by the properties of water and is not affected by air pressure.<ref>[https://fluidairedynamics.com/relative-humidity-vs-dew-point/ Fluid-Aire Dynamics, Inc. | Relative Humidity vs. Dew Point in Compressed Air Systems]</ref> After compressed air cools, then the vaporized water turns to liquefied water.<ref>[https://www.quincycompressor.com/why-dry-air-before-it-enters-air-compressor/ Quincy Compressor]</ref><ref>[https://www.atlascopco.com/en-ph/compressors/wiki/compressed-air-articles/what-is-condensate-in-air Atlas Copco | How can water harm my compressed air system?]</ref>

Cooling the air as it leaves the compressor will take most of the moisture out before it gets into the piping. Aftercooler, storage tanks, etc. can help the compressed air cool to {{cvt|104|F|C|order=flip}}; two-thirds of the water then turns to liquid.<ref>[https://www.quincycompressor.com/all-about-compressed-air-piping-systems/ Quincy Compressors | All About Compressed Air Piping Systems]</ref>

Management of the excessive moisture is a requirement of a compressed air distribution system. System designers must ensure that piping maintains a slope, to prevent accumulation of moisture in low parts of the piping system. Drain valves may be installed at multiple points of a large system to allow trapped water to be blown out.  Taps from piping headers may be arranged at the tops of pipes, so that moisture is not carried over into piping branches feeding equipment.<ref>[https://www.compressedairchallenge.org/library/articles/2012-06-CABP.pdf COMPRESSOR INLET PIPING by Hank van Ormer, Air Power USA, Compressed Air Best Practices, 06/2012 Page 26, column 2, Note 12.] {{webarchive|url=https://web.archive.org/web/20150910212035/http://www.compressedairchallenge.org/library/articles/2012-06-CABP.pdf |date=2015-09-10 }}</ref> Piping sizes are selected to avoid excessive energy loss in the piping system due to excess velocity in straight pipes at times of peak demand,<ref>{{cite web |url= http://www.tlv.com/global/TI/calculator/air-flow-rate-through-piping.html |title=Plant services (2005–2006 Collection) "Eliminate Mr. Tee" |page= 5 |url-status= live |archive-url= https://web.archive.org/web/20131124065652/http://www.tlv.com/global/TI/calculator/air-flow-rate-through-piping.html |archive-date= 2013-11-24 }}</ref> or due to turbulence at pipe fittings.<ref name="Merritt 2005">{{Cite magazine |url=http://www.compressedairchallenge.org/library/articles/Plant_Services%20_Compressed_Air_Articles.pdf |title=Top 10 Targets of a Compressed Air Audit |first=Rich |last=Merritt |magazine=Plant Services magazine |date=May 2005 |page=31 |url-status=dead |archive-url=https://web.archive.org/web/20161221233150/http://www.compressedairchallenge.org/library/articles/Plant_Services%20_Compressed_Air_Articles.pdf |archive-date=2016-12-21 }}</ref>

==See also==
{{div col}}
* {{annotated link|Air compressor}} 
* {{annotated link|Cabin pressurization}} 
* {{annotated link|Compressed air dryer}} 
* {{annotated link|Compressor}} 
* {{annotated link|Gas duster}} – (generally use fluorocarbons but some use compressed air.)
* {{annotated link|Rotary-screw compressor}} 
* {{annotated link|Air-line fitting}}
{{div col end}}

==Notes==
{{Reflist}}

==External links==
*{{Commons category-inline}}

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{{DEFAULTSORT:Compressed Air}}
[[Category:Compressed air power|.]]
[[Category:Breathing gases]]
[[Category:Gas technologies]]
[[Category:Energy storage]]
[[Category:Industrial gases]]
[[Category:Pneumatics]]
[[Category:Respiration]]