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Biological Chemistry

Periodic graphics: The chemistry of air fresheners

Chemical educator and Compound Interest blogger Andy Brunning sniffs out an answer to the question of whether air fresheners actually ‘kill’ bad odors

by Andy Brunning
February 19, 2018 | APPEARED IN VOLUME 96, ISSUE 8


To download a pdf of this article, visit

References used to create this graphic:

Molecule of the week: Cyclodextrins

How and why Febreze clears away stink

Take a whiff of chemistry

Cyclodextrins and their uses: a review

Is there danger from scented products?

A collaboration between C&EN and Andy Brunning, author of the popular graphics blog Compound Interest

To see more of Brunning’s work, go to To see all of C&EN’s Periodic Graphics, visit



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Joe Clark (February 21, 2018 5:01 PM)
Helpful and instructive quick read. Made me wonder about aromatherapy that’s becoming so popular.
Peter Wuts (February 21, 2018 6:17 PM)
Air fresheners just introduce VOC's into the air. Limonene and pinene can form hydroperoxides which are probably not good to breath. Maleic acid is a Michael acceptor and thus people may become sensitized to it. It is also known that it may accumulate in various organs. The best way to keep the air fresh is to keep the environment clean.
S. N. Balasubrahmanyam (February 22, 2018 2:03 AM)
The important thing is that essential oils and vaporisable materials with "pleasant" odours can only mask. The olfactory sensing process CAN identify the constituent odours in a mixture (I mean enabling distinctions such as "rotten egg" or "rancid butter" or "fecal", etc. from "jasmine", "lavender" and so on). Cyclodextrins are perhaps the best but for them to work the air needs to be circulated to "catch" the odoriferous materials.
Moon (August 25, 2018 9:20 AM)
What is the chemical equation of an air refreshener that is made of baking soda, water and essential oil?
Dr Walter Paget (February 24, 2018 2:22 PM)
To those if you who did chemistry in school, perhaps you remember some of the fundamental principles of gas kinetic theory? The rate of reaction between two gaseous species is proportional the the concentration of each. Bad odours are generally perceived at the ppb level. Air fresheners may get to ppm - depends on the volume being considered and rate of evaporation, temperature, etc. . Multiply the two together and you will approach a zero rate of reaction. In statistical terms, the reactants hardly ever meet, hardly ever have the required energy to react or find themselves in the preferred confirmation for reaction to take place. All marketing spiel. AFs can certainly paralyse your nasal epithelium (so you smell nothing) and can modify bad odours to be less offensive. As for formaldehyde formation, indeed this needs to be considered. But you probably get more exposure from your furniture as formaldehyde is ubiquitous. It is even in your bloodstream as a metabolite of normal biological processes!
Candles producing nano-carbon species I regard as a serious issue. Respirable particles are a bit different to “reactive carcinogen” (and formaldehyde is a class 3 carcinogen). Once they lodge in your lungs then they don’t move. Not at all like gas reactants that can diffuse away.
Having been a practical organic/ organometallic synthetic chemist and a VP in the perfume industry for 21 years and probably having breathing in more carcinogens than the average Joe, I put my trust in gas kinetic theory and blind luck. 65 years old and still going.
carlos pagos (February 24, 2018 9:09 PM)
It's a hard job for an added volatile chemical to do but there are many ways mechanical systems with simpler chemistry can work.

Some of these systems take advantage of the fact that the sense of smell indicates both to the concentration, and the differential of concentration.

Where possible it seems safer to treat the air using filters with activated charcoal / carbon or other substances like baking soda.

HVAC systems such as the smoke absorbers in fancy casinos have pretty good strategies.

UV is included in many HVAC filter systems.

Negative ions generators can reduce chemical odors "instantly". The trick is not to to add a lot of ozone.
M. Conley (June 10, 2018 12:38 PM)
I live in Las Vegas, where I understand to a degree why chemical air fresheners are used in casinos due to smoking. Unfortunately this is now pervasive in retail establishments as well. The smell penetrates paper products which is scary. I recently had to throw away a package of coffee filters (maybe I should have used them for dryer sheets?). I've also found that the smell can penetrate plastic packaging and sometimes the bread has a chemical odor and taste, and I can pull a plastic milk container out of the refrigerator that smells like the ever-popular sandalwood It makes no sense to buy organic produce if it's being soaked in chemicals. Yuck.

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