Autoclave

An autoclave is a sealed chamber that sterilizes medical and surgical items with steam under pressure. Raising the pressure allows steam to reach temperatures well above boiling — a common cycle runs at 121°C (250°F) at roughly 15 psi — hot enough to denature the proteins of every form of microbial life, including heat-resistant bacterial endospores that survive ordinary disinfection.

Proper operation is as important as the machine itself. Instruments must be cleaned first, wrapped in steam-permeable material, and loaded loosely so steam can circulate and contact every surface. Exposure time depends on the load: wrapped instrument packs require longer cycles than unwrapped items. After the cycle, packs must dry fully inside the chamber, since moisture wicks contaminants through wrapping, and sterilized packs are dated and stored so older packs are used first.

Quality assurance verifies that sterilization actually occurred. Chemical indicators — heat-sensitive tape and indicator strips placed inside packs — change color when sterilizing conditions are reached, while periodic biological indicators containing live resistant spores confirm the autoclave truly kills the hardest organisms. Autoclaving is the standard for sterilizing heat-stable instruments; items that cannot tolerate heat require chemical (cold) sterilization instead.

The CCMA exam tests autoclave operation in detail — wrapping, loading and unloading, cycle parameters, indicators, and quality assurance — within its minor surgery preparation content. The USMLE Step 1 draws on the same concept in microbiology, where autoclaving is the classic method for destroying bacterial spores.