Chemical sterilizers, often referred to as chemiclaves, typically use ethylene oxide (EtO) as the sterilizing gas.

Here's why EtO is commonly used:

* Highly effective: EtO is highly effective at killing a wide range of microorganisms, including bacteria, spores, fungi, and viruses.

* Penetrating: It can penetrate materials like plastics and fabrics, making it suitable for sterilizing medical devices and other items that cannot withstand high temperatures.

* Non-corrosive: EtO is relatively non-corrosive, making it safe for use with delicate instruments.

However, EtO is a potentially hazardous chemical and requires careful handling and disposal. It is a known carcinogen and can cause respiratory problems.

Note: While ethylene oxide is the most common gas used in chemiclaves, some newer models utilize alternative sterilization methods like hydrogen peroxide vapor or plasma sterilization, which are considered more environmentally friendly and safer to handle.