Dry heat sterilisation and depyrogenation
Dry heat sterilisation is widely used for glassware and materials that are not suitable for sterilisation using saturated steam. A range of temperatures and times are used. Currently a temperature of at least 170°C for 30-60 minutes is widely used. The term is not particularly precise since variable concentrations of water may be present.
In the absence of water, microbial destruction is relatively slow and it is generally accepted that oxidative effects have a major role in microbial destruction.
While microbial death can be modelled in a similar way to that described previously using saturated steam for microbial destruction the F value obtained is generally referred to as FH and a Tref of 170°C and a Z value of 20ºC are used.
Dry heat depyrogenation uses high temperatures to sterilise glassware and other materials and to destroy the biochemical activity of the pyrogen and endotoxin by products of microorganisms. The destruction of pyrogens and endotoxins can be modelled in a similar way to that described previously for microbial destruction using saturated steam but the F value obtained is generally referred to as FD and a Tref of 250°C and a Z value of 46.4ºC are used.