Why must oxygen cylinders, especially their valves, not be contaminated or come into contact with greasy substances?

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Oils, especially those containing unsaturated fats and fatty acids, easily vaporize and release heat. Oil-soaked yarn and oilcloth can catch fire on their own due to oxidation in the air; the heat generated does not dissipate, and when it reaches the ignition point, combustion occurs. Oils, on the other hand, vaporize more slowly in the air, and the heat generated is dissipated quickly; therefore, they generally do not accumulate heat to the point of self-ignition. Due to its extremely strong oxidizing property, pure oxygen can cause combustibles to burn violently. When oily substances come into contact with pure oxygen, their vaporization rate **increases**. A large amount of heat is released at the same time. The temperature rises rapidly, which will soon lead to combustion. If grease gets on the nozzle of an oxygen cylinder, the rapid release of oxygen causes the grease to undergo oxidation quickly. Moreover, the heat generated by the friction between the high-pressure gas stream and the nozzle further accelerates this oxidation process. As a result, grease attached to the oxygen cylinder or pressure regulator can lead to combustion, or even an explosion. This is why grease must absolutely not come into contact with oxygen cylinders, especially their nozzles and other components that come into contact with oxygen.