autoclaving
Autoclaving is sterilization with a pressure cooker. Inside a sealed chamber, water is boiled and the resulting steam is held under pressure so it can climb above its normal boiling point — typically to 121°C — and the wet, hot vapour kills even hardy bacterial spores. The classic cycle is 121°C held for 15 minutes after the load itself reaches temperature.
The magic is in the moisture. Saturated steam carries far more lethal energy than dry air at the same temperature, and when it touches a cooler surface it condenses, dumping its latent heat right where microbes live and wetting their proteins so they coagulate. This is why moist heat is faster and works at a lower temperature than dry heat. The cycle is monitored by temperature, pressure, time, and biological indicators carrying resistant spores.
Autoclaving is the preferred method for anything that can take heat and moisture: aqueous solutions in sealed containers, surgical instruments, glassware, rubber closures, gowns and dressings. Because it can be done on the sealed final container, it is a true terminal sterilization method.
Its limits are equally clear. Autoclaving cannot sterilize oils, fats or dry powders (steam cannot penetrate them), nor anything degraded by heat or water — heat-labile drugs, many proteins, and most plastics that would melt or distort.
Sealed bottles of normal saline are loaded into an autoclave and held at 121°C for 15 minutes; the steam penetrates the closure path and renders the finished product sterile in its own container.
Saturated steam under pressure: the standard, preferred way to terminally sterilize aqueous products.
The well-known 121°C/15 min is the reference cycle, but other equivalent combinations exist — for example 134°C for about 3 minutes — because higher temperature kills faster. Sealed solutions must also be cycled carefully so the internal pressure does not burst the container.