Now this may not be scientificly correct (don't rightly know) but aren't most atmospheres made up of percentages of different types of gasses??  I seem to remember most trek shows on hostile worlds (ahh, the science of those raised on T.V.  

 ) being hostile because the oxygen was way below par for earthers, and carbon dioxide etc was too high.  Now what would happen if a match was lit on a 80% methane world (with 15% oxy and 5% carbon) ??  Would this be a qualified BOOM?
  Just thoughts......
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"The Empress took your name away," said Chance.
Owen smiled coldly.  "It wasn't hers to take.  I'm a Deathstalker until I die.  And we never forget a slight or an enemy."  -Owen Deathstalker.