Steam sterilisation in an autoclave

Steam sterilisation is conducted inside of a pressure device – steam autoclave equipped with a thermostat, a manometer, and suitable safety valves.

The sterilising agent during steam sterilisation process is saturated steam under pressure in temperature 121°C (steam pressure around 2 bar) or in temperature 134°C (steam pressure around 3 bar). In order to achieve the full effect of steam sterilisation the sterilised material needs to be exposed to saturated steam under pressure for a certain time. All the surfaces of sterilised materials need to be in contact with the steam, therefore the sterilisation time depends on the size of the load and the type and density of sterilised material and takes between 20-30 minutes.

According to the European norm the sterilisation process needs to provide sterility assurance level SAL=10"6. This indicates that the risk of obtaining a non-sterile product is 1: 1000000.

The sterilisation process is a technological process composed of several tasks which lead to obtaining a sterile product. The process is performed so that each sterilisation results in a product of identical quality. Therefore the sterilisation process should be validated and routinely monitored and the autoclaves should be maintained in full operation.

Steam sterilisation is a universal, sure, fast, non-toxic and economic method.

Steam sterilisation process is composed of the following stages :

• The rise time – the interior of the autoclave is vented i.e. the air is removed and entirely replaced by saturated steam.
• The compensation time - after this period, the article to be sterilised has reached the required temperature at every point.
• The sterilisation phase - the duration is dependent on the sterilisation temperature and the microorganisms to be destroyed.
• The cool-down phase – the time needed for the pressure inside of autoclave to fall until it is the same as the atmospheric pressure.