Normally this takes place slowly. Raise the temperature and oxidation converts to burning. That is why pure oxygen should always be kept well clear of greases and oils, as oxidation can take place rapidly with petroleum products. The only lubricants that should ever be used on regulators or O-rings are those products specially designed for such use. The working area should also be cleared of all petroleum-based materials.
Acetylene is what chemists refer to as a triple bond molecule.
When the acetylene reaches kindling temperature, the bonds break and tremendous energy is released. The triple bond is why acetylene burns hotter than any other hydrocarbon gas when combined with oxygen. Acetylene is produced by combining calcium carbide with water. This is the same process that was used in miners lamps a century ago. A fuel leak involving acetylene is extremely hazardous.