Which of the following items may cause fire or explosion when working with nitrous oxide?

When working with nitrous oxide, it is important to recognize potential hazards that can lead to fire or explosions. One of the primary concerns with nitrous oxide is its ability to support combustion.

Oil and grease are both flammable substances, and when they come into contact with nitrous oxide, they can increase the risk of fire or explosion. Specifically, grease or oil around the valves of any tank can create a dangerous situation because these substances can ignite when exposed to high pressure or temperature, especially in an environment where nitrous oxide is present.

Moreover, while copper itself is not flammable, the lack of appropriate materials, such as copper tubing designated for gas distribution, can create problems in delivering gases safely and may result in leaks or ruptures in gas lines. Such failures can lead to hazardous conditions, particularly in the presence of flammable materials.

Taking all of these aspects into account, it becomes evident that working with nitrous oxide around any oil or grease, as well as ensuring proper distribution systems are used, is crucial for safety. Therefore, the correct response encompasses all these potential hazards, confirming that they can all contribute to a fire or explosion risk in a scenario involving nitrous oxide.