Final answer:
Ethylene oxide is used for sterilization of heat-sensitive objects, but due to its toxicity, gases like supercritical carbon dioxide are preferred for their safer properties.
Step-by-step explanation:
The oxide valuable for sterilization of heat-sensitive objects such as plastics, surgical and diagnostic appliances, and spices is ethylene oxide. Though it is highly effective as a sterilant due to its ability to permeate packaged materials and its efficient sterilization properties at low temperatures, its usage is carefully controlled because it is also recognized as explosive and carcinogenic. On the other hand, gases like supercritical carbon dioxide (scCO₂) are gaining popularity for commercial and medical sterilization due to their nonreactive, nontoxic, and nonflammable nature, effectively sterilizing at low temperatures without compromising the integrity of the materials being sterilized.