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It's a common claim on sites promoting beeswax candles over paraffin or soy candles that they "purify" the air and reduce allergies and asthma (Cleanup Expert,Ebeehoney, Pathways Arts, WarmCandle).

There does seem to be clear evidence that beeswax and soy wax burns cleaner than paraffin, that is, they produces less soot and volatile organic compounds (VOCs) (Rezaei et al). So it could be argued that compared to burning paraffin in your living space 24/7, using beeswax would improve air quality, but I don't think that's the argument being made when a website says, "When beeswax candles burn, they clean the air like a great, natural, air purifier." Ebeehoney

The method of "purification" is not always mentioned, although a few sites mention negative ions. It's unclear to me why beeswax would produce more negative ions than paraffin, and the only ion measurements that I was able to find on google scholar were for paraffin wax (Wright et al). In fact, this paper made it clear that ions are associated with soot, so my conclusion would be candles that soot more (i.e. paraffin) should have more negative ions.

Is there any basis to the claim that beewax candles purify the air?

Cecilia
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    There was [a 2007 study](http://www.eca-candles.com/pdf/Oekometric-Wax-1797_NCA_NL_42908.pdf) by the Bayreuth Institute of Environmental Research in Germany (Ökometric GmbH), apparently funded by the candle industry, which suggested that all types of candle emissions were low though not zero (presumably if you did not burn them for too long a time in an unventilated room); and that beeswax differed slightly from some others but not particularly in a way that was "better". – Henry Dec 22 '20 at 01:50
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    Meanwhile [a 2018 study of negative air ions and their effects on human health and air quality improvement](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6213340/) does not seem to suggest combustion or burning as a source of such ions. – Henry Dec 22 '20 at 01:57
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    +1 for this great question. Seems reminiscent of ads that claim you can save money by spending. Imagine how "pure" you can make the air by not burning anything at all. – Jerome Viveiros Dec 22 '20 at 07:52

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The study "Fine Particulate Matter Emissions from Candles" (viewable online) compared various candles. It found that the beeswax candle (called BW1 in the paper) emitted less PM2.5 (often considered the worst type of common air pollution) per wick than the paraffin candles, though it emitted far more when smouldering after being extinguished. The comparison is limited since the burn rate was not measured.

Since the air intake was filtered and none of the tests remained at 0 levels of PM2.5, particulate matter is added rather than removed from the air by beeswax candles. This study does not indicate anything about other types of air pollution. Since the claims from candle manufacturers/sellers are not more specific, we can't evaluate every possible thing beeswax candles might do. But they clearly produce PM2.5.

piojo
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    Hm.. I think it is undisputed that candles emit some amount of soot. It seems the claim is more about "reduce allergies and asthma", so the question is whether candles reduce any substances that might cause these, but this will probably not be covered by a study focussed on the emissions, using "clean" air to start with. – Hulk Dec 23 '20 at 09:35
  • @Hulk I agree with you that claims about exotic effects would not be tested by this experimental setup. But as I said, I didn't see more specific claims that could be evaluated. – piojo Dec 23 '20 at 17:07