The Apollo 1 astronauts died so fast and horribly because the capsule was highly Oxygen-enriched. Our dear Dr. Matrix is of course correct.
Oxygen assists combustion. Light a candle. What is really burning? Not the wick, the wick is wicking up the wax, just as it becomes soft and liquid enough to be wicked up by the wick, in what is generally known as…a wicking action.
The wax burns at the tip of the wick, and is allowed to burn by the presence of oxygen in both the wick, and wax, and the air around the candle.
Light a small candle. Get a big mayonnaise jar. ( This harkens back to what is now regarded as the Golden Age of The Straight Dope, when all fine scientific queries were answered at The Straight Dope Science Labs ). Light the candle, and put the long large jar over it, so it’s covered. Now, watch. The candle is nice and new, and would burn steadily until it is out of wax and wick, but for one major problem.
The candle is using the oxygen trapped in the sorta-sealed area under the mayonnaise jar. Once that oxygen has been depleted, the candle will slowly sputter and go out. It does not have enough oxygen to sustain its burn.
Not all things need lots of oxygen to burn. As AWB points out, even water can burn if it is in the right atmosphere. Magnesium burns very happily under water.
** The Flaming Cubes [b/]. BAND NAME !!!