Moist Heat

∞ generated and posted on 2016.02.05 ∞

Preferred, non-chemical route towards disinfection and sterilization of thermally stable materials.

Moist heat is both effective at lower temperatures and in many cases faster than the use of dry heat as a means of sterilization. On the other hand, to achieve sterilization, particularly in terms of eradication of endospores, somewhat complex apparatuses are required, particularly pressure cookers and their laboratory equivalent, autoclaves.

The key to successful disinfection or sterilization using heat is to bring the material being treated up to temperature. For large volumes, this can take time, even substantial amounts of time. With autoclaves, it is crucial that the high temperature steam reaches whatever surfaces are being treated and/or that liquids reach sufficient temperatures to achieve adequate killing. Then, once sufficient temperatures have been reached, they must be maintained for sufficient lengths of time.

Because autoclaves function by keeping water under pressure, the temperatures they are capable of reaching are a function of what pressures they reach, which can be easier to measure than temperatures. As a consequence, treatment conditions can be denoted in either pressures or temperatures. In terms of temperature, generally 121° C maintained for 15 min is sufficient to kill endospores, which translates to 100 KPa or 15 pounds per square inch (psi).