Fragrance-based air fresheners release more than 100 various chemicals into the air. These include volatile organic compounds like terpenes, which consist of substances such as limonene, alpha-pinene, and beta-pinene, as well as terpenoids like linalool and alpha-terpineol. Additionally, they contain other chemicals like ethanol, formaldehyde, benzene, toluene, and xylene, along with semi-volatile organic compounds, including phthalates.

Research on air freshener products has been conducted globally. In various studies that looked at different kinds of fragrance-based air fresheners, such as sprays, gels, solids, disks, oils, cartridges, diffusers, and evaporators—both active and passive—it was found that all these types can release significant amounts of volatile organic compounds. Interestingly, it seems that the makeup of the fragrance itself plays a bigger role in emissions than the method used to disperse it.

In research conducted in Germany on air fresheners, it was discovered that after one hour, the highest emission rates were observed for several compounds, including ethanol, dipropylene glycol mono methyl ether acetate, limonene, 2-propanol, 3-methoxy-3-methyl-1-butanol, benzyl acetate, dihydromyrcenol, iso-alkanes, linalool, linalyl acetate, gamma-terpinene, dipropylene glycol isomers, myrcene, and beta-pinene. Notably, limonene and linalool are identified as potential allergens. The study also highlighted that the most frequently emitted volatile organic compounds (VOCs) found in at least half of the tested products included limonene, linalool, myrcene, beta-pinene, alpha-pinene, linalyl acetate, dihydromyrcenol, geranyl acetate, and 4-methoxy-benzaldehyde. Therefore, the compounds that were both most prevalent and had the highest emission rates were limonene, linalool, myrcene, beta-pinene, linalyl acetate, and dihydromyrcenol.

Another research study focused on the emissions of volatile organic compounds (VOCs) from various air fresheners available in the United States, which included products like sprays, gels, solids, disks, and oils. The study found that the most frequently detected VOCs in at least half of these products were limonene, acetone, Triplal 1 (2,4-dimethyl-3-cyclohexene-1-carboxaldehyde), alpha-pinene, beta-pinene, 3-methyl-1-butanol acetate, Triplal extra (another form of 2,4-dimethyl-3-cyclohexene-1-carboxaldehyde), beta-phellandrene, a carene isomer, ethyl butanoate, and various forms of cymene (o, m, or p-cymene), along with ethanol. Notably, around 25% of the VOCs released from these products are considered potentially toxic or hazardous according to several federal regulations in the United States, raising concerns about air quality.

Surprisingly, in a research project examining the emissions of semi-volatile organic compounds (SVOCs) from air fresheners sold in the United States, which included options labeled as “all-natural” and “unscented,” it was found that 12 out of 14 tested products released phthalates. Among these, 10 products were found to emit phthalates in quantities ranging from at least 1 part per million (ppm) to as high as 7307 ppm.

Those air fresheners can be even more problematic because their emissions may interact with indoor oxidants like ozone, hydroxyl radicals, and nitrate radicals, leading to the formation of various oxidation products. For example, terpenes, which are primary emissions, can easily react with ozone, resulting in secondary pollutants such as formaldehyde, acetaldehyde, glycol ethers, and free radicals like hydroperoxy and alkyl peroxy radicals, as well as ultrafine particles. Several factors affect the emissions of these secondary pollutants, including the composition and concentration of ingredients, the reactive chemistry involved, and how the product is used.

For more information:

Volatile emissions from common consumer products | Air Quality, Atmosphere & Health (springer.com);

Impact of room fragrance products on indoor air quality – ScienceDirect;

NRDC: Clearing the Air – Hidden Hazards of Air Fresheners (pdf);

Ten questions concerning air fresheners and indoor built environments – ScienceDirect