Which method uses a gaseous sterilant for instrument sterilization?

• A. Ethylene oxide
• B. Hydrogen peroxide plasma
• C. Autoclave
• D. Dry heat

Answer: (A)

Gaseous sterilants work by using a gas to penetrate and sterilize instruments, especially those that are sensitive to heat or moisture. Ethylene oxide fits this role best because it’s a low-temperature gas that can infiltrate complex instruments and packaging, killing microorganisms—including spores—through alkylation. Cycles must be tightly controlled for temperature, humidity, and exposure time, and they require a thorough aeration phase to remove residual gas before use. In contrast, autoclaves and dry heat rely on heat transfer, not a gas, to sterilize. Hydrogen peroxide plasma uses vaporized hydrogen peroxide that is energized into plasma—effective at low temperature too, but it’s a different sterilization mechanism than a straightforward gaseous sterilant.