What is the common cycle of dry heat sterilization?

• A. 121 degrees C for 15 minutes
• B. 150-170 degrees C for minimum 2 hours
• C. 100 degrees C for 60 minutes
• D. 200 degrees C for 30 minutes

Answer: (B)

Dry heat sterilization relies on heat in a dry environment to inactivate microorganisms, and because dry air conducts heat less efficiently than steam, higher temperatures and longer exposure are required. In practice, a hot air oven used for dry heat typically uses around 150–170°C for about 2 hours. This duration ensures even the most heat-resistant microbes on instruments are killed without relying on moisture. The other options either reflect moist-heat conditions (such as 121°C for 15 minutes in an autoclave) or use temperatures/times outside the standard dry heat cycle, making them less reliable for achieving sterility. So, 150–170°C for a minimum of 2 hours is the common dry heat sterilization cycle.