Autoclave
From Wikipedia, the free encyclopedia
An autoclave is a device used
to sterilize equipment and supplies by subjecting them to high pressure
saturated steam at 121 °C for around 15–20 minutes depending on the size
of the load and the contents.[1]
It was invented by Charles Chamberland in 1879,[2]
although a precursor known as the steam digester
was created by Denis Papin in 1679.[3]
The name comes from Greek auto-, ultimately meaning self, and Latin clavis
meaning key—a self-locking device.[4]
Uses
Autoclaves are widely used in microbiology,
medicine,
tattooing,
body piercing, veterinary science, mycology, dentistry, and prosthetics
fabrication. They vary in size and function depending on the media to be
sterilized.
Typical loads include laboratory
glassware, other equipment and waste, surgical instruments and medical waste.[5]
A notable growing application of
autoclaves is the pre-disposal treatment and sterilization of waste material,
such as pathogenic hospital waste. Machines in this category largely operate
under the same principles as conventional autoclaves in that they are able to
neutralize potentially infectious agents by utilizing pressurized steam and
superheated water. A new generation of waste converters is capable of achieving
the same effect without a pressure vessel to sterilize culture media, rubber
material, gowns, dressing, gloves, etc. It is particularly useful for materials
which cannot withstand the higher temperature of a hot air oven.[6]
Autoclaves are also widely used to cure
composites and in the vulcanization of rubber.[7]
The high heat and pressure that autoclaves allow help to ensure that the best
possible physical properties are repeatably attainable. The aerospace industry
and sparmakers (for sailboats in particular) have autoclaves well over 50 feet
(15 m) long, some over 10 feet (3.0 m) wide.[citation needed]
Air
removal
It is very important to ensure that
all of the trapped air is removed from the autoclave before activation, as hot
air is a very poor medium for achieving sterility. Steam at 134 °C can achieve
in three minutes the same sterility that hot air at 160 °C can take two
hours to achieve.[8]
Methods of achieving air removal include:
Downward displacement (or gravity-type): As steam enters the chamber, it
fills the upper areas first as it is less dense than air. This compresses the
air to the bottom, forcing it out through a drain which often contains a
temperature-sensing device. Only when air evacuation is complete does the
discharge stop. Flow is usually controlled by 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: air dilution by using a series of steam pulses, in which
the chamber is alternately pressurized and then depressurized to near
atmospheric pressure.
Superatmospheric cycles: achieved with a vacuum pump. It starts with a vacuum
followed by a steam pulse followed by a vacuum followed by a steam pulse. The
number of pulses depends on the particular autoclave and cycle chosen.
Subatmospheric cycles: similar to the superatmospheric cycles, but chamber
pressure never exceeds atmospheric pressure until they pressurize up to the
sterilizing temperature.
Autoclaves
in medicine
A medical autoclave is a device that
uses steam
to sterilize equipment and other objects. This means that all bacteria,
viruses,
fungi,
and spores
are inactivated. However, prions, such as those associated with Creutzfeldt-Jakob
disease, may not be destroyed by
autoclaving at the typical 134 °C for three minutes or 121 °C for 15 minutes[citation needed]. Also, some organisms, such as the archaeon Geogemma barosii, can survive at temperatures above 121 °C.
Autoclaves are found in many medical
settings, laboratories, and other places that need to ensure the sterility of
an object. Many procedures today employ single-use items rather than
sterilizable, reusable items. This first happened with hypodermic needles, but today many surgical instruments (such as forceps,
needle holders, and scalpel
handles) are commonly single-use rather than reusable items (see waste autoclave).
Because damp
heat is used, heat-labile products (such as some plastics)
cannot be sterilized this way or they will melt. Paper and other products that may be
damaged by 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 become more common as an alternative
to incineration due to environmental and health concerns raised because of
the combustion by-products emitted by 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 waste.
In Dentistry, autoclaves provide
sterilisation of dental instruments according to health technical memorandum
01-05 (HTM01-05). According to HTM01-05, instruments can be kept, once
sterilised using a vacuum autoclave for up to 12 months using sealed pouches. [9]
Autoclave
quality assurance
Sterilization bags often have a "sterilization indicator mark"
that typically darkens when the bag and its contents have been adequately
processed. Comparing the marks on an unprocessed bag (L) and on a bag that has
been properly cycled (R) will reveal an obvious visual difference.
There are physical,
chemical,
and biological
indicators
that can be used to ensure that an autoclave reaches the correct temperature
for the correct amount of time.
Chemical indicators on medical packaging and autoclave tape
change color
once the correct conditions have been met, indicating that the object inside
the package, or under the tape, has been appropriately processed. Biological
indicators contain spores of a heat-resistant bacterium, Geobacillus stearothermophilus. If the autoclave does not reach the right temperature, the
spores will germinate when incubated and their metabolism
will change the color of a pH-sensitive chemical. Some physical indicators consist of an alloy designed to melt only after being
subjected to a given temperature for the relevant holding time. If the alloy
melts, the change will be visible.
Some computer-controlled autoclaves
use an F0 (F-nought) value to control the sterilization cycle. F0 values are set for the number of
minutes of sterilization equivalent to 121 °C (250 °F) at 100 kPa
(15 psi) above atmospheric pressure for 15 minutes . Since exact
temperature control is difficult, the temperature is monitored, and the
sterilization time adjusted accordingly.
The entire wiki link on the subject can be found at: https://en.wikipedia.org/wiki/Autoclave
Poster's comments:
Those that use pressure canners for food preparation and
storing use a form of an autoclave, too. The link has images of simple stovetop
autoclaves.
Bottom line, boiling about anything is a good way to kill
germs and viruses. Steaming under pressure only enhances achieving the
objective or goal, but simple boiling does just fine, too.
Now in the case of food preparations and storing, I do
recommend following the directions as they are well intended, and generally
also do a very good safe job.
2 comments:
Manufacturers, Exporters, Suppliers of Autoclave Sterilizer, Laboratory Equipments, Lab Equipment, Medical Autoclave, Industrial Oven, Bod Incubator Bioreactors, Growth Chambers for Lab, Industry and Research Organization.
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Autoclaves Sterilizers
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