Which of the following is not considered a hazardous gas material?

Diesel fuel is not classified as a hazardous gas material, which is why it is the correct answer. While diesel fuel is flammable and can pose various safety concerns, it primarily exists as a liquid at room temperature and does not present the same immediate gas-related hazards as the other options listed.

Chlorine, hydrogen, and anhydrous ammonia are all gases at room temperature and exhibit toxic, corrosive, or reactive properties that can pose significant health risks and require specialized handling and mitigation strategies during emergencies. The classification of materials as hazardous gas usually involves considerations of their state at room temperature, toxicity, and potential to cause harm in case of leaks or exposure, which is why those other substances are deemed hazardous gases.