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The dry heat sterilization process is accomplished by conduction; that is where heat is absorbed by the exterior surface of an item and then passed inward to the next layer. Eventually, the entire item reaches the proper temperature needed to achieve sterilization.
Moist heat sterilization processes sterilize using hot air that is heavily laden with water vapor, which plays the most important role in the sterilization. [ 1 ] [ 2 ] Boiling a sample for 30 minutes or more will kill virtually all vegetative cells present, but will not kill spores , which can germinate shortly thereafter and resume growth.
Dry heat sterilizer. Dry heat was the first method of sterilization and is a longer process than moist heat sterilization. The destruction of microorganisms through the use of dry heat is a gradual phenomenon. With longer exposure to lethal temperatures, the number of killed microorganisms increases.
They are much smaller than autoclaves but can still be as effective. They can be more rapid than an autoclave and higher temperatures can be reached compared to other means. As they use dry heat instead of moist heat, some pathogens like prions, may not be killed by them every time, based on the principle of thermal inactivation by oxidation.
Sterilization using steam can also be done at a temperature of 132 C (270 F), at a double pressure. [citation needed] Dry heat sterilization is performed at 170 C (340 F) for one hour or two hours at a temperature of 160 C (320 F). Dry heat sterilization can also be performed at 121 C, for at least 16 hours. [17]
It is designed specifically to prove that the process achieved full temperature and time required for a normal minimum cycle of 134 °C for 3.5–4 minutes. [20] To prove sterility, biological indicators are used. Biological indicators contain spores of a heat-resistant bacterium, Geobacillus stearothermophilus.
A process flow diagram (PFD) is a diagram commonly used in chemical and process engineering to indicate the general flow of plant processes and equipment. The PFD displays the relationship between major equipment of a plant facility and does not show minor details such as piping details and designations.
Inspissation is the process used when heating high-protein containing media; for example to enable recovery of bacteria for testing. Once inspissation has occurred, any stained bacteria, such as Mycobacteria, can then be isolated. A serum inspissation or fractional sterilization is a process of heating an article on 3 successive days as follows: