Which substance must be kept away from high-pressure oxygen to prevent an explosion?

• A. Oil
• B. Water
• C. Grease
• D. Dust

Answer: (A)

In environments with high-pressure oxygen, ignition risk for flammable materials spikes because the available oxygen is extremely concentrated and heat that might be tolerable in normal air can become enough to sustain rapid combustion. Oil is a classic hazard here because it forms a combustible film on surfaces and can ignite from a small spark or heat source much more readily when oxygen is abundant. Once oil catches fire in a high-oxygen setting, the reaction can escalate quickly into an explosion due to the powerful oxidizer present. Water, by contrast, is not flammable and tends to absorb heat, helping to suppress flames rather than fuel them. Dust can also pose an explosion risk in oxygen-rich atmospheres if finely dispersed, but the direct, well-known risk from the options given is oil, which is why it must be kept away to prevent an explosion.