Are you serious? Do you have any clue how many candles you'd have to have burning for how long in a very small (sealed) room to have any noticeable effect on oxygen levels? Personal experience with this?
When I was young my hobby was collecting candles before I made my way into flashlights. Using whatever allowance I have, I can fill a 14' by 18' room with candles until I'm left with a 2' wide walkway in the middle...this was when I was 8, I'm 22 now
Come to think of it I can't really prove that it could be hazardous, but I do remember I had the worst headaches whenever I might multiple candles in an enclosed room, but I never got tired of seeing fire dancing beside me so I never quit from it. I've always thought it was the CO/CO2 levels increasing, guess not:candle:
Either way, leaving a candle burning unattended in an enclosed room is generally a bad idea, I've always been warned that under low levels of oxygen any flame source will begin to emit carbon monoxide, or CO...colorless, tasteless, but deadly. But since LukeA so generously calculated the resultants, I'll edit it out
For centuries before electricity people used cnadles and lanterns for light inside their houses, and I can't seem to recall any widespread reports of people passing out or dying from high carbon dioxide levels (and no, they didn't leave their windows cracked in the middle of winter either).
I don't think centuries ago people used caulk under doors and windows, uses multi-layer insulation in walls...what I'm getting to is that modern houses are pretty well sealed compared to ones built 10 years ago...let alone 100