Question
Autoclave
Answer
An autoclave is the standard device for moist heat sterilization under pressure, the most reliable and widely used sterilization method in medical/laboratory practice.
Principle: raising pressure above atmospheric raises the boiling point of water correspondingly — steam under pressure (15 lbs/sq inch) reaches 121°C; held for 15–20 minutes, this combination of high temperature, moisture, and pressure kills all microorganisms, including the most heat-resistant bacterial spores, by denaturing and coagulating their proteins.
Construction: a double-walled chamber; steam is generated (internally or supplied externally) and admitted, displacing air (which must be fully evacuated — via a discharge valve or vacuum pump — for the set temperature to be reliably achieved throughout the load); a pressure gauge, safety valve, and thermometer monitor conditions; a timer controls the holding period.
Standard cycle: 121°C at 15 lbs/sq inch for 15–20 minutes.
Uses: sterilization of surgical instruments, dressings, culture media, glassware, rubber goods, and laboratory/hospital waste. Not suitable for heat/moisture-damaged materials (some plastics, sharp instruments, oils/powders steam cannot penetrate).
Sterility monitoring: chemical indicators (autoclave tape, Bowie-Dick test) and biological indicators (Geobacillus stearothermophilus spore strips, which must show no growth after processing) confirm that true sterilizing conditions were achieved throughout the load.