Answer to Question #258189 in Microbiology for Lole

Question #258189
  1. List the 4 parameters involved in steam sterilization. (2 marks).
  2. What is the difference between “saturated steam” and “super-heated steam”? (3 marks)
  3. How is “dry air” removed from the autoclave in the beginning of the cycle? (2 marks)
  4. State the functions of the following parts of the autoclave: (6 marks) Safety Valve 1: Safety Valve 2 : Vacuum Release Valve:
  5. State 4 precautions that need to be taken when autoclaving “liquid media” in a bottle? (4 marks)
  6. What is the purpose of using an ”autoclave tape”? (2 marks)
  7. How much water should be added to the autoclave before you start the sterilization process? (1 mark)
Expert's answer

1. The basic principle of steam sterilization, as successful in an autoclave, is to expose each item to direct steam contact at a required temperature and pressure for the specific time. There are 4 parameters of steam sterilization:

- Steam

- Pressure

- Temperature

- Time

These parameters can be manipulated into different cycles hot sterilization f various type of loads.

2. When we heat the water even after the boiling then water vaporises into steam or water in a gaseous or vapour form.

Saturated stem is generated when water is heated to the boiling point.

Duper-heated steam is generated when water is heated above the saturation point.

3. Air must be removed from the chamber and the load before direct steam contact and sterilization can occur. This is accomplished in a steam sterilizer by a series of vacuum pulses prior to sterilization (pre-conditioning phase).

4. Safety valves are generally caribrated in shuch a way that they will release the pressure if it exceeds some critical value. The safety devices are very useful to avoid accidents due to undesirable high pressure which may mount due to non-attendance of the operator. Because of its large safety role, it is important that you ensure your safety valve is tested before usage and is regularly inspected and maintained. Vacuum Release Valve is used to create a pre-vacuum, prior to autoclave operation. Vacuum systems are designed to replace air present inside the chamber with steam. It does this in two phases: pre-vacuum, where it removes air by pulling a vacuum on the chamber before the cycle, and post-vacuum, where it pulls a vacuum after the cycle in order to remove remaining steam within the chamber. Vacuum systems are not present in all autoclaves, as usually, only certain types of autoclaves have them.

5. Precautions that need to be taken when autoclaving “liquid media” in a bottle

- the bottle must be filled with liquid media maximum on 2/3 of its volume

- the bottle must be plugged with cotton plug

- the neck of the glass bottle must be covered with foil or a paper cap in order to prevent unplugging during intensive boiling of the liquid media

- after autoclaving, pressure must be released very slowly in order to avoid intensive boiling of liquid media in a bottle

6. The purpose of using an ”autoclave tape” is to control the efficiency of autoclaving. This tape changes its color to dark at some critical temperature.

7. Water should be added to the autoclave in such a volume that totally covers the heating elements of the autoclave.

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