How Does Autoclave Pressure Affect Sterilization?

by dewi susanti

Optimum autoclave pressure is a key component in the sterilization process. In fact, the term autoclave describes a mechanism that locks shut automatically, when the internal pressure rises. This locking mechanism is part of the safety features of the device, which prevents accidental spraying out of steam. Such steam, under high pressure, is vital for the destruction of harmful microbes.


The Unique Role Of Autoclave Pressure


autoclave pressureBasically, an autoclave is quite similar to a pressure cooker. This is because autoclave pressure is derived from the action of steam within the device. This steam, under high pressure, then becomes the main sterilizing agent. Without the presence of high pressure, steam within autoclaves would not reach high temperature levels necessary for it to destroy harmful pathogens.

High autoclave pressure enables steam to derive greater heat from the latent heat of vaporization – the heat required to convert boiling water into steam – rather than the heat required to raise the temperature of water. This is a critical aspect, since the latent heat of vaporization is dramatically higher than the heat necessary to raise water temperature. For instance, boiling 1 litre of water requires 80 Kcal. (kilo calories), whereas converting a similar quantity of water into steam requires 540 Kcal.

There is also a unique action of steam at the surface level of objects being sterilized. Normally, a negative pressure is created on the surface of cooler objects as steam contacts such surfaces and condenses (such condensation creates a dramatic loss in steam volume). The negative pressure resulting from such steam contact on cold surfaces draws in more steam to the specific area. This type of action enables complete sterilization of all external surfaces in an object placed within the autoclave chamber.


Standard Autoclave Pressure And Temperature

Generally, high temperature processes with short operation periods are more preferred than lower temperature processes that last for longer periods. This is due to the greater effectiveness of the high temperature – short period processes. However, there are various basic standard temperature and pressure values. These include: 121 Deg. C at 15 psi (pounds per square inch), 115 Deg. C at 10 psi and 132 Deg. C at 27 psi. When measuring the time taken to sterilize an object within the autoclave, the starting time should be measured from the moment it reaches normal operating pressure and temperature.


Precautions To Ensure Correct Autoclave Pressure

Due to the critical role of internal pressure in the sterilization process, various precautions must be taken to safeguard this key feature. Firstly, the autoclave should have appropriate pressure and temperature for each object under sterilization.

Take note that, pressure within an autoclave chamber cannot penetrate through tightly wrapped packages. Such tightly packed wrapping would hold cool air pockets that will reduce efficiency of the sterilization process. In order to counter this issue, a bag that contains items for sterilization should have some water added into it. Such water would produce steam within the bag that may displace air from it.

The presence of steam at very high pressure and temperature within an autoclave necessitates various safety precautions for all users of the device. Such safety precautions must necessarily involve wearing of protective personal equipment (eye goggles, heat resistant gloves and lab coats).

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