Nonanal in the bedroom

At a glance

What it is

Nonanal is a simple straight-chain aldehyde, nine carbons long, with a characteristic fatty, waxy, citrus odour. It is a workhorse of flavour and fragrance — known in perfumery as Aldehyde C-9 — occurs naturally in citrus peel and more than two hundred foods, and is used as a permitted flavouring at the level of a few parts per million. Industry — The Good Scents Company In other words, it is a low-toxicity molecule you have eaten and smelled countless times; its interest here is not poison but ubiquity.

What makes nonanal matter indoors is that the same fatty-acid chemistry that puts it in citrus also produces it from oxidising materials. Straight-chain aldehydes such as hexanal, octanal and nonanal are routinely detected in indoor air as the fatty acids in wood, foams and oils slowly oxidise. Peer-reviewed — Maddalena et al. 2009, Environ. Sci. Technol.

How it relates to the bedroom

The smell of "new"

A great deal of "new furniture," "new car," and "new mattress" smell is aldehydes, and nonanal is one of the most recognisable. A 2009 study of temporary housing units measured emissions from their materials and found that nonanal was one of just two compounds — alongside formaldehyde — whose modelled indoor concentrations exceeded chronic reference exposure levels or odour thresholds, traced to composite wood, sealants and vinyl coverings. Peer-reviewed — Maddalena et al. 2009 For nonanal, whose odour threshold is very low, the most plausible reading of that result is that you smell it long before it reaches a toxic level. Inferred — nonanal's low odour threshold means threshold exceedance most likely reflects odour

Made in your breathing zone

Nonanal also has a second, more intimate source. When indoor ozone reaches the thin film of oil on your skin — and on the surfaces around you — it reacts with squalene and unsaturated fatty acids to generate a family of aldehydes and carbonyls right in your breathing zone. Peer-reviewed — Wisthaler & Weschler 2009, PNAS Nonanal is among the aldehydes this skin-ozone chemistry can yield, though it is harder to pin down individually than markers like 6-MHO because of measurement overlap. Inferred — nonanal's specific skin-ozone yield is not cleanly resolved in the source measurements The same study noted that some of these skin-ozone products can act as respiratory or skin irritants. Peer-reviewed — Wisthaler & Weschler 2009

Smell as a signal, not a verdict

Nonanal is the clearest case in the Atlas of a compound whose importance is sensory. Because the nose registers it at a tiny fraction of any toxic concentration, a strong fatty-citrus "new" smell is best read as a cue that a room needs airing, not as evidence of a dangerous exposure. Inferred — odour detection far below toxicological thresholds That is a useful reframing: ventilation answers the smell and the (small) exposure at the same time.

What the research says

• It is a ubiquitous material-emitted indoor aldehyde. From wood panels, sealants, vinyl and foam; flagged with formaldehyde for exceeding reference levels or odour thresholds. Peer-reviewed — Maddalena et al. 2009
• It also forms from skin–ozone chemistry. Ozone plus skin lipids yields aldehydes and carbonyls, some irritant. Peer-reviewed — Wisthaler & Weschler 2009
• It is a low-toxicity, permitted flavouring. Naturally in citrus and many foods; used in flavours at low ppm. Industry — flavour/fragrance documentation
• Its dominant indoor role is odour. Detectable far below any toxic level. Inferred

What helps reduce it

Ventilate. Fresh-air exchange is the main control — it clears nonanal along with the rest of the new-material and new-foam emissions.

Air out new furnishings and foam. Unwrapping and ventilating new wood furniture, mattresses and foam in a well-aired space speeds the fade of the aldehyde smell.

Don't add ozone. Avoid ozone-generating "air purifiers" — ozone reacting with skin and surface lipids is one of the ways nonanal and related aldehydes are produced indoors. Peer-reviewed — Wisthaler & Weschler 2009

What does NOT help

• Treating the smell as a measure of danger. Nonanal is detectable far below any toxic level; the odour is a prompt to ventilate, not evidence of harm. Inferred
• Masking it with fragrance. Adding scented product layers more reactive VOCs into the room without removing the aldehyde. Inferred

Open research questions

• Nonanal's specific contribution to the skin-ozone aldehyde burden in the bedroom, given the measurement overlap that complicates its identification. Speculation
• The health relevance, if any, of chronic low-level exposure to mixtures of straight-chain aldehydes indoors. Speculation

Citations

1. Maddalena R, Russell M, Sullivan DP, Apte MG (2009). Formaldehyde and other volatile organic chemical emissions in four FEMA temporary housing units. Environmental Science & Technology, 43(15):5626–5632. DOI 10.1021/es9011178 (PMID 19731654). Via PubMed. Peer-reviewed
2. Wisthaler A, Weschler CJ (2009). 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. DOI 10.1073/pnas.0904498106 (PMID 19706436). Via PubMed. Peer-reviewed
3. The Good Scents Company. Nonanal (Aldehyde C-9), CAS 124-19-6 — flavour and fragrance identity: a fatty, citrus aldehydic odorant naturally present in citrus and many foods, used as a permitted flavouring at low ppm. thegoodscentscompany.com Industry

Frequently asked questions

• What is that "new furniture" or "new car" smell, and is nonanal part of it?

  Straight-chain aldehydes like hexanal, octanal and nonanal are a big part of it. Nonanal in particular has a strong fatty, citrus-like odour and is released from composite wood (particleboard and MDF), sealants, vinyl, and foam as the fatty acids in those materials slowly oxidise. Because the human nose detects nonanal at very low concentrations, it contributes to the "new" smell well before it reaches any level of toxicological concern.

• Is nonanal harmful?

  Nonanal is low in toxicity. It is a permitted flavouring substance, occurs naturally in citrus and over 200 foods, and is used in flavours at a few parts per million. Its relevance indoors is mostly as an odorant and mild irritant rather than a systemic-toxicity or cancer concern. In one housing-unit study, nonanal was flagged alongside formaldehyde as exceeding chronic reference levels or odour thresholds — for nonanal, with its very low odour threshold, that most plausibly reflects smell rather than a toxic dose.

• Where does the nonanal in my bedroom come from?

  Several places at once: it off-gasses from wood-based panels, sealants, vinyl and foam as their fatty-acid content oxidises; it forms from cooking-oil oxidation and is emitted by vehicle interiors; and it is generated in your breathing zone when indoor ozone reacts with the lipids on your skin and on surfaces. It is one of the most ubiquitous aldehydes in indoor air.

• How do I reduce nonanal?

  Ventilation is the main lever: fresh-air exchange clears nonanal along with the rest of the new-material and new-foam emissions, and airing out new furniture or a new mattress in a well-ventilated space speeds the fade. Avoiding ozone-generating devices also helps, because ozone reacting with skin and surface lipids is one of the ways nonanal and related aldehydes are formed indoors.

Related compounds

• Acetaldehyde — a smaller, higher-concern aldehyde in the same new-foam emission family
• 6-MHO — the cleaner marker of the skin-ozone chemistry nonanal also takes part in
• Limonene — another odour-forward VOC whose ozone chemistry matters more than its toxicity
• BHT — a fellow low-concern, smell-and-dose foam emission
• Alpha-pinene — the pine-scent terpene whose ozone chemistry forms secondary particles

Embr is a sleep environment company researching and addressing the chemistry of the bedroom. Research and product development in progress.

Last reviewed 2026-06-27. If you find a factual error, contact us.