How does a hot air oven work?

• A. Uses moist heat to destroy the cytoplasm of cells
• B. Uses dry heat to destroy the cytoplasm of cells
• C. Uses chemical sterilants
• D. Uses radiation to sterilize

Answer: (B)

Hot air ovens sterilize by dry heat. They heat and circulate air inside the chamber to transfer heat without moisture, which gradually dehydrates and oxidizes microbial cells. This damages proteins and cellular structures, ultimately destroying the organisms. Because dry heat transfers heat less efficiently than moist heat, higher temperatures and longer exposure are needed compared with steam sterilization. Other methods—chemical sterilants or radiation—use chemical actions or ionizing energy, not dry heat. So the mechanism is dry heat to destroy the cytoplasm of cells.