From article: There are other mechanisms that might render the Earth uninhabitable by our kind of life. Over geological time, the partial pressure of oxygen in

From article: There are other mechanisms that might render the Earth uninhabitable by our kind of life. Over geological time, the partial pressure of oxygen in the atmosphere has risen. With more solar energy inputs, it may be that oxygen levels continue to soar. Above about 28%, even waterlogged biomass will burn handily: and there are indications that atmospheric oxygen (currently down around 16%) has been well over 20% in the past. If oceanic photoautotrophs pump out too much of the stuff, the continents may well be burned back to bedrock by the resulting lightning-triggered fires. I get that more oxygen in the atmosphere = a potentially combustible atmosphere. What I'm a little confused about is why we never hear about spontaneous greenhouse fires? Wouldn't the presence of all those leafy greens push large amounts of oxygen into the (relatively) closed local atmosphere? or is the innate ventilation to the outside world from a not purposely constructed vacuum environment enough to offset the potential dangers of this? I assume it must be or we'd at least occasionally hear of greenhouses resulting in explosions?