Grammar usage

I disagree with Lewis.  Can has at least 2 meanings: (1) ability, or (2) permission.  When I was a child, growing up in Saskatchewan, Canada, whenever I would ask a permission question using can, my father would rhetorically reply, "I don't know, can you?", which meant that I was using the wrong verb to ask for permission to do something.  In fact, the limitation of can to ability-only contexts is an old wives' tale.  In other words, it is not true.  You can use can to ask for permission.

When you are asking for permission to do something, you can use may, can, or could.  May and could are more formal, and thus more polite, than can but all three are acceptable. 

May I use your washroom?

Could I use your washroom?

Can I use your washroom?

I hope this helps.

'May' is used to ask permisission, and 'can' is used to ask ability.

'May' is proper in your sentence, unless the lack of oxygen might prevent combustion, unlikely in this case.

'Can I climb that tree?' This is asking someone if they believe I am physically capable of climbing the tree.

Language changes over time. Lewis gives the formal, technically correct -- albeit somewhat outdated -- answer. Shawn gives an answer that reflects actual usage today, although most formal references reject the usage as sloppy.

From my reading, British English (including the Canadian variant) appears to be more accepting of can used to ask permission than does American English. Still, one hears the usage more often than not in America.