What is the typical gas concentration range used in gas sterilization?

• A. 50-150 mg/L
• B. 100-400 mg/L
• C. 200-800 mg/L
• D. 900-1200 mg/L

Answer: (C)

Gas sterilization relies on a potent gas, typically ethylene oxide, whose ability to kill microorganisms depends on concentration along with temperature, humidity, and exposure time. The gas concentration used is in the hundreds of milligrams per liter, with a typical operating range of about 200–800 mg/L. This window achieves reliable kill, including spores, while balancing material compatibility and safety concerns from residuals and operator exposure. If the concentration is too low, sterilization may be incomplete; if it’s too high, there’s greater risk of damaging sensitive materials and increasing toxic residues that require longer aeration. Lower ranges like 50–150 mg/L are often insufficient for robust sterilization, while very high ranges such as 900–1200 mg/L add unnecessary risk and complications.