Provided they can withstand moist heat under pressure,  Solid and Porous loads are usually best sterilised using saturated steam sterilisation. The load is treated uniformly to very tight temperature tolerances – control is by fast responding pressure sensors. The fixed relationship between steam temperature and pressure allows this pressure control to manage the treatment temperature very accurately.

The steam condenses on the load, as it does so it releases latent heat which sterilises the load. New steam is precisely injected into the chamber to make up for the condensation and maintain the required pressure.  Steam quality is important. The control assumes the chamber holds saturated steam, free of air and non-condensable gases, and with a tightly controlled dryness fraction. Over-dry superheated steam might not condense and release latent heat; over-wet steam would already be partly condensed, reducing its effectiveness. Air removal and steam conditioning are subject to tightly controlled regulations and ongoing controls such as air detection.

This is the most reliable means of sterilising solid goods such as filling line change parts, porous loads including textiles, fine-bore tubing or bagged items, assemblies incorporating delicate membrane filters where pressure gradients need careful management to avoid damaging the filters, media in open containers , where pulsed air removal may need to be replaced by gravity displacement methods.to avoid over-boiling of pre-warned media, fluids and freeze-dried products contained in small glass vials or ampoules.