Medical equipment needs to be sterilised to prevent the spread of infection before it can be used. An autoclave is a device that sterilises medical equipment. Autoclaves are also used by tattoo and piercing artists to sterilise needles. The autoclave developed as an extension of the research done with pasteurisation processes.
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History of Sterilization
Between 460 and 377 B.C. Hippocrates cleaned surgical instruments by pouring boiling water over them. Between 1729 and 1799 Italian biologist Lazzaro Spallanzani discovered that bacteria died after being heated in sealed glass flasks for 30 minutes. On April 20, 1862 Louis Pasteur conducted the first series of tests in which liquids where heated in pressurised containers to sterilise them. This became known as pasteurisation and is still used to preserve milk, juice and other foodstuffs. Charles Chamberland, who worked with Pasteur to develop pasteurisation, developed the autoclave in 1879.
What is an Autoclave?
In its most basic form the autoclave is a pressure cooker. Water is heated in a pressurised environment to create steam. Using pressure makes it possible to heat to higher temperatures with less energy. Autoclaves are usually made of steel and have various configurations for removing air prior to pressurisation. Downward displacement autoclaves use gravity to remove air. Steam pulsing autoclaves use pulses of steam along with pressurising and depressurising to reach optimum pressure. Vacuum pump autoclaves suck air out for pressurisation. Superatmospheric autoclaves are a combination of steam pulsing and vacuum pump techniques.
How Does an Autoclave Work?
An autoclave sterilises items by heating them with steam to a very high temperature. Some common temperatures at which autoclaves operate are: 46.1 degrees C C/10 p.s.i., 49.4 degrees C C/15 p.s.i., and 55.6 degrees C C/27 p.s.i. (p.s.i.=pounds per square inch). The temperature, pressure and time of operation depend on the degree of sterilisation needed.
What Does an Autoclave Kill?
An autoclave using standard settings can kill most bacteria, spores, viruses and fungi. However, most prions are not killed by an autoclave using standard settings and some organisms can survive at temperatures above 120 degrees C. Most doctor's offices, tattoo parlours, dentist offices and other places where instruments might come in contact with contaminants have a small autoclave on site for disinfection. Hospitals use larger autoclaves that look similar to industrial dishwashers to sterilise many items at once. Heat kills microorganisms by causing vital proteins to coagulate. The proteins stick together causing fatal damage to the microorganism. An autoclave cooks microorganisms in the same way a pressure cooker cooks food, but at a higher temperature. Autoclaves use steam instead of dry heat because steam can more effectively transmit heat to the microorganisms.
Other Uses for Autoclaves
An autoclave can also be used in the manufacture of chemicals that require pressure and high heat, such as dyes.
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