Ethylene oxide (ETO) gas is the preferred sterilization method for heat-sensitive medical instruments such as endoscopes because it operates at low temperatures (30-60°C), preventing damage to delicate materials and electronics. Unlike autoclaving or dry heat, which require high temperatures, ETO effectively penetrates complex device lumens and packaging to ensure comprehensive sterilization. It is highly effective against all microorganisms, including spores, without compromising the integrity or function of sensitive instruments. Hence, ETO maintains the sterility and longevity of heat-labile medical equipment.

Reference: Principles and Practice of Infectious Diseases, Mandell, Douglas, and Bennett, 9th Edition.