Autoclave 251401 222944500 2008-07-01T21:18:46Z 129.81.181.102 /* Chemiclave */ {{For|the early 1990s indie rock band based in Washington, D.C.|Autoclave (band)}} {{For|the cipher|Autokey cipher}} {{Infobox Laboratory equipment |name = Autoclave |image = Sapphire.jpg |caption = A modern front-loading autoclave |acronym = |other_names = |uses = [[Sterilization (microbiology)|Sterilization]] |inventor = [[Charles Chamberland]] |manufacturer = |model = |related = [[Waste autoclave]] }} An '''autoclave''' is a [[pressure vessel|pressurized device]] designed to heat aqueous solutions above their [[boiling point]] to achieve [[sterilization (microbiology)|sterilization]]. It was invented by [[Charles Chamberland]] in [[1879]].<ref name=Ref1>{{cite web |url=http://www.pasteur.fr/infosci/archives/chb0.html |title=Chronological reference marks - Charles Chamberland (1851-1908) |accessdate=2007-01-19 |last=|first=|authorlink= |coauthors= |date= |year=|month=|format= |work= |publisher=Pasteur Institute |pages= |language= |archiveurl= |archivedate= |quote= }}</ref> The term '''autoclave''' is also used to describe an industrial machine in which elevated temperature and pressure are used in processing materials. == Introduction == Under ordinary circumstances (at [[standard pressure]]), liquid [[water]] cannot be heated above approximately 100 °C (99.99 °C at 101.325 kPa, 99.62 °C at 100 kPa) in an open vessel except for [[superheated steam|special situations]]. Further heating results in [[boiling]], but does not raise the temperature of the liquid water. However, when water is heated in a sealed vessel such as an autoclave, it is possible to heat liquid water to a much higher temperature. As the container is heated the [[pressure]] rises due to the constant [[volume]] of the container (see the [[ideal gas law]]). The boiling point of the water is raised because the amount of [[energy]] needed to form [[steam]] against the higher pressure is increased. == Air removal == When the goal of autoclaving is to achieve sterility, it is very important to ensure that all of the trapped [[air]] is removed. The reason for this is that hot air is very poor at achieving sterility. Steam at 134 °C can achieve in 3 minutes the same sterility that hot air at 160 °C takes two hours to achieve. Autoclaves may achieve air removal by various means including: '''Downward displacement''' (or gravity type) - As steam enters the chamber, it fills the upper areas as it is less dense than air. This compresses the air to the bottom, forcing it out through a drain. Often a temperature sensing device is placed in the drain. Only when air evacuation is complete discharge should stop. Flow is usually controlled through the use of a steam trap or a solenoid valve, but bleed holes are sometimes used, often in conjunction with a solenoid valve. As the steam and air mix it is also possible to force out the mixture from locations in the chamber other than the bottom. '''Steam pulsing''' - Some autoclaves remove air by using a series of steam pulses, in which the chamber is alternately pressurized and then depressurized to near atmospheric pressure. '''Vacuum pumps''' - Some autoclaves use vacuum pumps to suck air or air/steam mixtures from the chamber. '''Superatmospheric''' - This type of cycle uses a vacuum pump. It starts with a vacuum followed by a steam pulse and then a vacuum followed by a steam pulse. The number of pulses depends on the particular autoclave and cycle chosen. '''Subatmospheric''' - Similar to superatmospheric cycles, but chamber pressure never exceeds atmospheric until they pressurize up to the sterilizing temperature. == Uses == Autoclaves are widely used in [[microbiology]], [[medicine]], sterilizing instruments for [[body piercing]], [[veterinary science]], [[dentistry]], [[podiatry]] and [[metallurgy]]. The large [[carbon-fiber]] [[composite material|composite]] parts for the [[Boeing]] [[Boeing 787|787]], such as [[wing]] and [[fuselage]] parts, are cured in large autoclaves.<ref name=Ref2>{{cite web |url=http://www.heraldnet.com/stories/07/04/29/100bus_speed001.cfm |title=Up to Speed |accessdate=2007-04-30 |last=Kageyama |first=Yuri |authorlink= |coauthors= |date=2007-04-29 |year=|month=|format= |work= |publisher=heraldnet.com |pages= |language= |archiveurl= |archivedate= |quote= }}</ref> == Autoclaves in medicine == [[Image:Autoclave stove top.jpg|thumb|300px|right|Stovetop autoclaves - the simplest of autoclaves]] A medical autoclave is a device that uses [[steam]] to [[sterilization (microbiology)|sterilize]] equipment and other objects. This means that all [[bacterium|bacteria]], [[virus]]es, [[fungi]], and [[spore]]s are inactivated. However, [[prion]]s, like those associated with [[Creutzfeldt-Jakob disease]], also may not be destroyed by autoclaving at the typical 121 degrees Celsius for 15 minutes or 134 degrees Celsius for 3 minutes, but can be destroyed with a longer sterilization cycle of 134 degrees Celsius for 18 minutes{{Fact|date=December 2007}}. Autoclaves are found in many medical settings and other places that need to ensure sterility of an object. Many procedures today use single-use items rather than sterilized, reusable items. This first happened with [[hypodermic needles]], but today many [[surgical instruments]] (such as [[forceps]], [[hypodermic needle|needle]] holders, and [[scalpel]] handles) are commonly single-use items rather than reusable. See [[waste autoclave]]. Because [[humidity|damp]] heat is used, [[lability|heat-labile]] products (such as some [[plastics]]) cannot be sterilized this way or they will melt. Some [[paper]] or other products that may be damaged by the [[steam]] must also be sterilized another way. In all autoclaves, items should always be separated to allow the steam to penetrate the load evenly. Autoclaving is often used to sterilize medical waste prior to disposal in the standard [[municipal solid waste]] stream. This application has grown as an alternative to [[incineration]] due to environmental and health concerns raised by combustion byproducts from incinerators, especially from the small units which were commonly operated at individual hospitals. Incineration or a similar thermal oxidation process is still generally mandated for pathological waste and other very toxic and/or infectious medical wastes. ==Chemiclave== Unlike the [[humid]] environment produced by conventional [[steam]], the [[saturation (chemistry)|unsaturated]] [[chemical]] [[vapor]] method is a low-humidity process. No time-consuming drying phase is needed, because nothing gets wet. The heat-up time is shorter than for most steam [[sterilization (microbiology)|sterilizers]], and the heaters stay on between cycles to minimize warm-up time and increase the instrument turnover. ==Autoclave quality assurance== [[Image:Autoclaves.jpg|thumb|250px|right|Multiple large autoclaves are used for processing substantial quantities of laboratory equipment prior to reuse, and infectious material prior to disposal. The machine in the middle is a washing machine, the machine to the right is the Autoclave]] [[Image:Sterilization bag indicator mark.jpg|thumb|200px|left|Sterilization bags often have a “sterilization indicator mark” that typically darkens when sterilization temperatures have been reached. Comparing the mark on an unprocessed bag to a bag that has been properly cycled will show an obvious visual difference.]] There are [[physics|physical]], [[chemistry|chemical]], and [[biology|biological]] [[pH indicator|indicators]] that can be used to ensure an autoclave reaches the correct [[temperature]] for the correct amount of [[time]]. [[Chemical]] [[indicators]] can be found on [[medical]] [[packaging]] and [[autoclave tape]], and these change [[color]] once the correct conditions have been met. This color change indicates that the object inside the package, or under the tape, has been autoclaved sufficiently. Biological indicators include attest devices. These contain [[spores]] of a heat-resistant bacterium, ''[[Geobacillus stearothermophilus]]''. If the autoclave does not reach the right temperature, the spores will [[germination|germinate]], and their [[metabolism]] will change the color of a [[pH]]-sensitive chemical. Physical indicators often consist of an [[alloy]] designed to melt only after being subjected to 121°C or 249°F for 15 minutes. If the alloy melts, the change will be visible. In addition to these indicators, autoclaves have timers, temperature and [[pressure gauge]]s that can be viewed from the outside. There are certain [[plastics]] that can withstand repeated temperature cycling greater than the 121°C or 249°F required for the autoclaving process. [[Perfluoroalkoxy|PFA]] and PP (#5) are examples. Some computer-controlled autoclaves use an F<sub>0</sub> (F-naught) value to control the [[sterilization (microbiology)|sterilization]] cycle. F<sub>0</sub> values are set as the number of minutes of equivalent sterilization at 121°C or 249°F (e.g: F<sub>0</sub> = 15 min.). Since exact temperature control is difficult, the temperature is monitored, and the sterilization time adjusted accordingly. ==See also== *[[Aerated autoclaved concrete]] *[[Pressure cooking|Pressure cooker]] *[[Sterilization (microbiology)]] *[[Waste autoclave]] ==References== {{reflist}} ==External links== * [http://www.guardian.co.uk/uk_news/story/0,3604,1019156,00.html Strain 121] {{Laboratory equipment}} [[Category:Laboratory equipment]] [[Category:Medical equipment]] [[Category:Medical hygiene]] [[Category:Microbiology equipment]] [[de:Autoklav]] [[es:Autoclave]] [[et:Autoklaav]] [[fr:Autoclave]] [[it:Autoclave]] [[lt:Autoklavas]] [[nl:Autoclaaf]] [[ja:オートクレーブ]] [[no:Autoklav]] [[pl:Autoklaw]] [[pt:Autoclave]] [[ru:Автоклав]] [[fi:Autoklaavi]] [[sv:Autoklav]] [[uk:Автоклав]]