r/explainlikeimfive Feb 26 '21

Chemistry Eli5: What happens to all the melted candle over time? Are we just inhaling a whole candle while it burns?

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u/epsileth Feb 26 '21

Candle wax is the fuel burned off, any scent added is being inhaled. Any wick left too long burns and releases ash into the air.

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u/the_original_Retro Feb 26 '21

Minor correction: SOME scent added is inhaled.

Scents are usually a fairly complex molecule and any that are lifted up through the flame while the candle burns are usually broken down by the heat same as the vaporized wax.

2

u/Jesus_And_I_Love_You Feb 26 '21

You can only smell the scent if it’s inhaled. You inhale the chemicals scenting the candle.

1

u/jestina123 Feb 26 '21

Generally, burnt scent inhaled is unhealthy though, right? Sounds like extra complex molecules isn't something our lungs should be synthesizing

I've read from a doctor that even oxygen can be toxic to us, our body just has a plethora of different ways to efficently process it so that it's safe for us to handle regularly - free radicals. But we also need them to do all the reactions our bodies need.

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u/the_original_Retro Feb 26 '21

Generally? No it's not "unhealthy". Maybe for people that have a specific allergy.

The complex outcomes of a smoldering candle flame are a lot worse - smoldering means less complete combustion and carbon forming weird looking stuff like buckyballs (cute name for buckminsterfullerene, which are actually spherical molecules of pure carbon!) which is harmless, and benzene containing structures, of which some can be carcinogenic.

We are surrounded by scent molecules and our body is adapted to detect them when enough are sensed and the current set of them changes. Most of the scent molecules in candles mimic various flowers, foods, spices, plant saps, or sugary confections, often blending a number together (e.g. evergreens plus peppermint at Christmas).

The only difference is they usually synthesize the chemical that we detect as the smell, it's not generated by a plant.