Air fresheners are consumer products that typically emit fragrance and are used in homes or commercial interiors such as restrooms, foyers, hallways, vestibules and other smaller indoor areas, as well as larger areas such as hotel lobbies, auto dealerships, medical facilities, public areas and other large interior spaces. Car fresheners are used in automobiles. As a source of odours, specific deodorizing blocks are made for toilets and urinals.

In this post, Pritish Kumar Halder illustrates air freshener basic principles and other properties 

There are many different methods and brands of air fresheners. Some of the different types of air fresheners include electric fan air fresheners, gravity drip hygiene odour control cleaning systems, passive non-mechanical evaporating aroma diffusers, and metered aerosol time-operated mist dispensers, sprays, candles, oils, gels, beads, and plug-ins.

Some air fresheners contain chemicals that provoke allergy and asthma symptoms or are toxic. Air freshening is not only limited to modern-day sprays, air freshening also can involve the use of organic and everyday household items. Although air fresheners are primarily used for odour elimination, some people use air fresheners for the pleasant odours they emit.

Basic principles

The control of odors is addressed by five classes of mechanisms;

1)Adsorption: Adsorbents like zeolite, activated charcoal, or silica gel may be used to remove odors.

2)Oxidation: ozone, hydrogen peroxide, peroxide, chlorine, chlorate and other oxidizing agents can be used to oxidize and remove organic sources of odors from surfaces and, in the case of ozone, from the air as well.

3)Air sanitizer: Odors caused by airborne bacterial activity can be removed by air sanitizers that inactivate bacteria.

4)Surfactants and soaps

5)Masking: Overwhelming an odor with another odor by any of the means described above.

Delivery of the above air freshener mechanisms falls into two broad categories: continuous action and instant action. Continuous action products include scented candles and devices which use a candle flame or some other heat source to heat and vaporize a fragrance formulation, incense burners, wall plug-ins which either use piezoelectric technology to aerosolize fragrance or heat to vaporize it,

Fragrance impregnated gels which release fragrance as the gel evaporates sometimes with the help of an electric fan, wick and reed diffusers which release fragrance by evaporation from fragrance-soaked wicks or wooden reeds; and fragrance impregnated materials like floor wax, paper, plastics, wood which release fragrance by off gassing; and lastly nebulization systems which convert liquid fragrances into a vapor in a cold process without the use of heat.


In addition to the adsorbents, oxidizers, surfactants, and disinfectants listed above, ingredients in air fresheners can include fragrances, aerosol propellants, preservatives, and solvents such as mineral oil or 2-butoxyethanol and other glycol ethers. As fragrances, air freshener preparations often include terpenes such as limonene.

A report issued in 2005 by the Bureau European des Unions de Consommateurs (BEUC) found that many air freshener products emit allergens and toxic air pollutants including benzene, formaldehyde, terpenes, styrene, phthalate esters, and toluene.

In 2020 air fresheners (as well as cleaning solutions and products used to clean cars) will need to list any of their ingredients which are on California’s list of 2,300 harmful chemicals, based on a California law passed in 2017. A California study in 2006 found that the prominent products of the reaction of terpenes found in air fresheners with ozone included formaldehyde, hydroxyl radical, and secondary ultrafine particles. It is not clear if manufacturers will need to list such chemicals which are not ingredients, but form when the air freshener is placed in the air.


Many air fresheners employ carcinogens, volatile organic compounds and known toxins such as phthalate esters in their formulas. A Natural Resources Defense Council (NRDC) study of 13 common household air fresheners found that most of the surveyed products contain chemicals that can aggravate asthma and affect reproductive development. The NRDC called for more rigorous supervision of the manufacturers and their products, which are widely assumed to be safe.