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Good Question
Just saying, maybe go easy with the candelabras.
By Randall Munroe
Where does a candle go when it burns, anyway? Is it healthy to be breathing in melted candle particles? How concerned should I be?
— Abigail B., Washington, D.C.
When candles burn, most of their matter goes into the air.
The light and heat from a candle comes from the wax burning. When you light the wick, the flame causes some of the wax to melt, flow up the wick and evaporate, and then the wax vapor burns. The wick, which is made of cotton, also burns, although it’s the wax that contributes most of the heat. The puddles you sometimes see around the base are from wax that spilled and dripped down without burning.
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Wax is made of hydrogen and carbon. When a candle burns, the hydrogen and carbon from the wax combine with the oxygen in the air to become carbon dioxide and water vapor. Most of the matter in the candle ends up as these two gases.
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Carbon dioxide and water aren’t exactly safe — too much of either can be extremely dangerous, as anyone who’s been on a submarine can tell you — but at low levels they are normal parts of the air. The amount of each gas produced by a candle is small — comparable to the amount that might be breathed out by another person in the room.
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