In what condition must oxygen cylinders be kept regarding oil and grease?

Oxygen cylinders must be maintained in a condition that ensures safety from fire hazards, as oxygen supports combustion. Keeping them at least 20 feet away from oil or greases is vital because any contamination of oxygen with these materials can lead to a dangerous reaction. Oil and grease can ignite explosively when in contact with high concentrations of oxygen, significantly increasing the risk of a fire or explosion.

By maintaining this distance, it reduces the likelihood of any accidental ignition and supports compliance with safety regulations. This practice is crucial in preventing accidents and ensuring a safe working environment around high-pressure oxygen equipment. The other options do not align with safe handling practices for oxygen cylinders; for instance, regularly oiling or handling cylinders without regard for contamination would compromise safety.