Which device sterilizes articles using steam under pressure?

• A. Ultrasonic cleaner
• B. Autoclave
• C. Refrigerator
• D. Oven

Answer: (B)

Steam under pressure is what makes an autoclave effective for sterilization. An autoclave seals items inside and exposes them to saturated steam at high pressure, which raises the temperature to levels that reliably kill all microorganisms, including spores. The moist heat penetrates wrapped items and complex instruments, ensuring thorough sterilization. Typical cycles run around 121°C (250°F) under pressure for about 15–20 minutes, though shorter cycles at higher temperatures are also used in modern models.

In contrast, an ultrasonic cleaner uses high-frequency waves in a liquid to loosen dirt and debris, not to sterilize. A refrigerator lowers temperature to slow microbial growth, preserving rather than sterilizing. An oven applies dry heat without steam or pressure, which is less effective for sterilization of many items and takes longer.