What is the common cycle of gas sterilization?

• A. 25-40 degrees C with RH 50% and gas concentration of 100-300 mg/L for 2 hours
• B. 30-60 degrees C with RH 30% and gas concentration of 200-800 mg/L for 3 hours
• C. 15-25 degrees C with RH 60% and gas concentration of 400-1000 mg/L for 4 hours
• D. 30-60 degrees C with RH 30% and gas concentration of 200-800 mg/L for 3 hours

Answer: (D)

Gas sterilization relies on a balance of temperature, humidity, gas concentration, and exposure time to allow the sterilant to diffuse into materials and inactivate microorganisms without damaging them. Ethylene oxide cycles are typically run at moderate temperatures to facilitate diffusion, with controlled humidity to enhance the sterilant’s reactivity, a practical concentration range, and a few hours of exposure to ensure thorough penetration. The described cycle—30-60°C, around 30% relative humidity, gas concentration of 200–800 mg/L, for about 3 hours—fits this common, well-established set of parameters. The other options deviate in temperature, humidity, concentration, or duration in ways that are less typical or less reliable for achieving consistent sterilization of standard loads.