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Author Topic: Does burning candles improve air quality?  (Read 2568 times)

Offline thedoc

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Does burning candles improve air quality?
« on: 30/10/2015 14:50:01 »
Giulio asked the Naked Scientists:
   Hi there,
I was wondering if burning candles indoor can improve the air quality inside a house/apartment.
Thanks in advance.
Cheers
What do you think?
« Last Edit: 30/10/2015 14:50:01 by _system »


 

Offline alancalverd

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Re: Does burning candles improve air quality?
« Reply #1 on: 30/10/2015 16:18:56 »
No. High quality air contains only oxygen and nitrogen with a hint of water and CO2. Burning anything increases  CO2, decreases O2, and adds soot and volatile materials to the mix, none of which is good for you.

"Cooks' candles" absorb strong odours but you are just substituting one chemical  pong for another.
 
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Offline evan_au

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Re: Does burning candles improve air quality?
« Reply #2 on: 30/10/2015 23:50:53 »
Many smelly organic chemicals are flammable, so if they pass by a flame, they are likely to be broken down into non-smelly chemicals like H2O and CO2. However, they are also likely to  produce more noxious substances like NOx and SO2.

Incomplete burning of the wax can also create nanoparticles of soot, which may find their way deep into your lungs and cause irritation.

But if you are so familiar candles that you "like" the smell, or you find them "romantic", then you probably will overlook some of the negatives.
 
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Offline Bored chemist

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Re: Does burning candles improve air quality?
« Reply #3 on: 31/10/2015 13:25:53 »
Many smelly organic chemicals are flammable, so if they pass by a flame, they are likely to be broken down into non-smelly chemicals like H2O and CO2.
True, but if even half the air in the room had been through a candle flame then half the oxygen would be missing from the air.
You would be dead
 

Offline evan_au

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Re: Does burning candles improve air quality?
« Reply #4 on: 01/11/2015 03:56:53 »
Quote from: Bored Chemist
if even half the air in the room had been through a candle flame then half the oxygen would be missing from the air.
You would be dead
I agree with this as a statement of chemistry, but not as a statement of physics.

A 100g candle, with an average composition of Cn/sub]H2n will consume all the oxygen in 1.2m3 of air (according to my rough calculations). The rate-limiting step is melting and wicking the wax into the flame.

But if 0.0001% of this air consisted of smelly volatiles, far more than 1.2m3 of air would pass by the flame in the course of convection. Any volatiles in this air heated to flashpoint would be combusted, and the amount of oxygen consumed would still be 1.2m3 of air.

So you would be no more dead than just burning a 100g candle - but the room might smell slightly different (but not necessarily better!).
 

Offline evan_au

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Re: Does burning candles improve air quality?
« Reply #5 on: 01/11/2015 04:16:13 »
I vaguely recall that many smelly organics contain double bonds, and these tend to have a lower flashpoint than organics of similar size with just single bonds.

This is independent of the smelly organics which contain sulphur: allyl methyl sulphide produced from eating garlic contains both sulphur & double bonds.

http://www.science20.com/chemical_etiquettes/smelly_chemicals_organic_chemists_view-110206
 

Offline alancalverd

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Re: Does burning candles improve air quality?
« Reply #6 on: 01/11/2015 08:46:48 »
But the smell of garlic improves the quality (or at least the price) of restaurant food and keeps the vampires away. Who would want to get rid of it?
 

Offline Bored chemist

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Re: Does burning candles improve air quality?
« Reply #7 on: 01/11/2015 14:22:37 »
Quote from: Bored Chemist
if even half the air in the room had been through a candle flame then half the oxygen would be missing from the air.
You would be dead
I agree with this as a statement of chemistry, but not as a statement of physics.

A 100g candle, with an average composition of CnH2n will consume all the oxygen in 1.2m3 of air (according to my rough calculations). The rate-limiting step is melting and wicking the wax into the flame.

But if 0.0001% of this air consisted of smelly volatiles, far more than 1.2m3 of air would pass by the flame in the course of convection. Any volatiles in this air heated to flashpoint would be combusted, and the amount of oxygen consumed would still be 1.2m3 of air.

So you would be no more dead than just burning a 100g candle - but the room might smell slightly different (but not necessarily better!).
That seems to me to be a rather long winded way of pointing out that most of the air in the room doesn't go through the flame, so most of the odourants in the air couldn't be destroyed en route though that flame.
Hardly at odds with what I said.
Did you see that I started my post with the word "if"?
 

Offline wolfekeeper

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Re: Does burning candles improve air quality?
« Reply #8 on: 01/11/2015 16:48:44 »
Burning candles does the opposite of improving air quality.

A burning candle involves incomplete burning of paraffin (essentially diesel) oil.

That produces a whole mess of toxic chemicals, soot, nanoparticles, carbon monoxide etc. None of which are remotely good for you; they're seriously bad for you in fact.

But sure, yes, your place will smell nicer.
 

Offline Janechem

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Re: Does burning candles improve air quality?
« Reply #9 on: 11/11/2015 06:54:58 »
Burning candle will produce negative influence to the environment of the room. But it won't decrease the oxygen amount of the room as there is air ventilation and the room is not sealed.  ;D
 

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Re: Does burning candles improve air quality?
« Reply #9 on: 11/11/2015 06:54:58 »

 

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