Tecknojock
Keeping the world running
I was under the impression that everything would catch on fire before it got to that concentration
Oxygen toxicity is a problem for diving, especially with nitrox. A partial pressure of 1.6 Bars of oxygen will cause immediate effects, so say roughly a dive of 6m on 100% oxygen. A partial pressure of .5 Bars of oxygen can cause long term vascular damage for long exposures. The latter would be a 50% oxygen mixture at sea level.
A high oxygen level by itself won't cause combustion, it just increases the likely hood of an explosion due to rapid combustion if something catches fire.