At a glance
| Chemical family | Saturated aldehyde — C8 straight-chain (caprylaldehyde / n-octanal) |
| CAS number | 124-13-0 |
| Classification | Not classified by IARC. Sensory irritant at elevated concentrations. A natural product of lipid oxidation. EU CLP not harmonised — some self-classifications include Flam. Liq. 3, Skin Irrit. 2, Eye Irrit. 2 |
| Where you encounter it | Indoor air from skin oil oxidation (ozone + skin lipids); material emissions from wood, paper, textiles, linoleum; food flavouring (citrus peel); natural component of many essential oils |
| Sleep micro-environment relevance | Produced directly during sleep from ozone-skin lipid reactions. One of the aldehydes that increases in bedroom air during occupied periods. Part of the 'occupied room' VOC profile |
Regulatory & certification status
| European Union | REACH registered substance. Not harmonised under CLP. No indoor air quality guideline. EFSA approved as a food flavouring substance. Regulatory |
| United States | FDA GRAS as a food flavouring. No EPA indoor air quality guideline. No OSHA occupational exposure limit. Regulatory |
| Canada | No Health Canada indoor air quality guideline for octanal. Regulatory |
| International | Not IARC classified. WHO does not set indoor air quality guidelines for individual aldehydes other than formaldehyde and acetaldehyde. Regulatory |
What it is
Octanal is an eight-carbon saturated aldehyde with a citrus-fatty odour. It occurs naturally in citrus peel oils and is used as a food flavouring and fragrance ingredient. In the indoor environment, octanal has two main sources. First, it is emitted from building materials — wood, paper products, natural fibre textiles, and linoleum all release octanal as a product of the autoxidation of their constituent fatty acids. Second, and particularly relevant to the bedroom, octanal is produced by the ozone-initiated oxidation of human skin lipids. When ozone in indoor air reacts with squalene and unsaturated fatty acids on the skin surface, it produces a characteristic suite of aldehydes — primarily 6-MHO and 4-OPA, but also octanal, nonanal, and decanal. IARC has not evaluated octanal. It is a mild irritant at elevated concentrations but is not classified as a carcinogen or reproductive toxicant.
Where it shows up in bedding
Octanal is produced in the bedroom through a reaction that occurs literally on the sleeper's body. During sleep, indoor ozone reacts with squalene and unsaturated fatty acids on the skin surface and in sebum absorbed into pillowcases and sheets. This reaction generates octanal (along with nonanal, decanal, 6-MHO, and 4-OPA) directly in the breathing zone. Chamber studies have shown that bedroom aldehyde concentrations rise during occupied sleep periods and fall when the room is unoccupied. The effect is proportional to ozone concentration — bedrooms with higher ozone ingress (ground floor, open windows near traffic) produce more oxidation products. Using ozone-depleting ventilation filtration or reducing ozone sources reduces octanal production during sleep.
Citations
- Wisthaler, A. and Weschler, C.J. (2010). Reactions of Ozone with Human Skin Lipids: Sources of Carbonyls, Dicarbonyls, and Hydroxycarbonyls in Indoor Air. Proceedings of the National Academy of Sciences, 107(15): 6568-6575. Source Peer-reviewed
- Weschler, C.J. (2016). Roles of the Human Occupant in Indoor Chemistry. Indoor Air, 26(1): 25-40. Source Peer-reviewed
- ECHA. Octanal — Substance Information. Source Regulatory
Frequently asked questions
Why does my bedroom smell different in the morning?
The change in bedroom air chemistry overnight is partly due to aldehydes like octanal produced by ozone reacting with skin lipids. During sleep, your body continuously produces squalene and fatty acids on the skin surface, and indoor ozone reacts with these to create aldehydes that accumulate in the bedroom air. This contributes to the 'occupied room' smell that dissipates with ventilation.
Can I reduce aldehyde production during sleep?
Yes. Since octanal and related aldehydes are produced by ozone-skin lipid reactions, reducing indoor ozone is the most effective control. Keeping windows closed during high-ozone periods (typically afternoon), using activated carbon filtration, and ventilating the bedroom in the morning after waking all help. Showering before bed reduces the skin lipid load available for oxidation.
Related compounds
Embr is a sleep environment company researching and addressing the chemistry of the bedroom. Research and product development in progress.
Last reviewed 2026-07-08. If you find a factual error, contact us.