Validating autoclaves

16 Feb

When the temperature and moisture content do not match up, two things can happen: 1) If the moisture content is higher than saturation for the temperature, wet loads occur, as discussed previously.

2) When the moisture content is lower than saturation for the temperature, the condition is called superheat.

As with wet steam, the Sterility Assurance Level will be less than expected if non-condensable gas content has increased since product sterility validation.

The percentage of non-condensable gases in the steam should be less than or equal to 3.5% by volume.

These physical aspects include temperature (superheat), dryness (liquid water content), and non-condensable gas content.

In general, this is not defined, rarely measured, and, if discussed at all, is relegated to the mythology of sterilizer arcana.

With the release of EN 215, the bar has been raised.

The acceptance criteria are shown in the following table. Steam dryness is calculated by measuring the temperature change in a known amount of water in relation to the mass of steam that is required to cause that temperature change.

Ideally, the temperature rise is exactly proportional to the amount of steam delivered to the water to heat it, resulting in a dryness value of 1.0 (i.e.

perfectly dry steam with no liquid water content.) Normally, the dryness value is less than 1.0, as there are thermal losses in any piping system even if it is well insulated.