At a glance
| Chemical family | Volatile organic compound — a chloromethane (the simplest chlorinated hydrocarbon, CH₃Cl) |
| CAS number | 74-87-3 |
| Classification | IARC Group 3 (not classifiable as to carcinogenicity to humans) |
| Where you encounter it | New polyurethane and memory-foam off-gassing; an industrial intermediate; and a large natural atmospheric background (oceans, biomass burning, vegetation) |
| Sleep micro-environment relevance | One of the four compounds making up ~81–95% of a new memory-foam mattress's total VOC output — and one of the slowest to fade (emission half-life ~24 days) |
| Activated carbon capture | Limited — small and volatile; ventilation over the first weeks does more than filtration |
What it is
Chloromethane (methyl chloride, CH₃Cl) is the simplest chlorinated hydrocarbon — one chlorine atom on a methane backbone. It is a gas at room temperature, used industrially as a chemical intermediate, and notably it is also the most abundant halogen-containing organic compound in the natural atmosphere, produced in large quantities by oceans, biomass burning, and plants.
On hazard, IARC classifies chloromethane as Group 3 — not classifiable as to carcinogenicity to humans. Peer-reviewed — IARC Group 3 Its known toxicology at high exposures is neurological: methyl chloride affects the central nervous system at high occupational concentrations. Those concentrations are far above anything a bedroom reaches from a mattress.
How it relates to the bedroom
One of the four dominant foam VOCs
The 2022 memory-foam study found that four compounds — 2-propanol (isopropanol), acetone, chloromethane, and toluene — together accounted for roughly 81% to 95% of total VOC emissions from the two mattresses tested over the first year. Peer-reviewed — Beckett et al. 2022, PMID 35588879 Chloromethane is one of those four.
The one that lingers
Here is what makes chloromethane worth its own page. The same study measured how fast each compound's emissions decayed. Isopropanol and acetone had half-lives of hours — gone almost immediately. Chloromethane and toluene were different: their emission half-lives were on the order of 24 days. Peer-reviewed — Beckett 2022 In plain terms, chloromethane is the slow tail of the new-foam smell — the part still present weeks after you unwrap the mattress. This is the single most useful fact for setting expectations: "off-gassing" is not a one-day event; the persistent components take weeks of ventilation to clear.
There is always a natural background
Because chloromethane is the most abundant natural halocarbon in the atmosphere, your indoor air contains some regardless of any product. The mattress adds to that background temporarily. This is context that keeps the picture honest — it is not a compound that only exists because of foam.
What the research says
Below health benchmarks
The memory-foam study's overall conclusion applies here: the measured and modeled concentrations of total VOCs and of the individual compounds, chloromethane included, were below available health-based screening levels, leading the authors to judge the mattresses unlikely to pose a consumer health risk. Peer-reviewed — Beckett 2022 The relevance of chloromethane here is its persistence, not acute hazard.
Honest scope
We flag chloromethane because of what it teaches about timing, not because the bedroom levels are alarming. The integrity move is to say both things plainly: it lingers for weeks, and the measured levels are low. Inferred — persistence makes ventilation duration matter more than peak concentration
What helps reduce it
Ventilate over weeks, not just the first day. Because chloromethane's half-life is ~24 days, the sensible response to a new mattress is sustained airflow over the first several weeks — open windows, a fan, air exchange — rather than a single airing.
Air out a new mattress before first use if you can. Even a few days of off-gassing in a ventilated space removes the early peak.
Keep the bedroom ventilated generally. Fresh-air exchange is the dominant lever for all the persistent foam VOCs together.
What does NOT help
- Expecting the smell to vanish in a day. The fast components do; chloromethane and toluene do not. Plan for weeks.
- Relying on a carbon filter alone for a small volatile gas. Ventilation removes chloromethane more effectively than passive filtration.
Open research questions
- How much chloromethane decay rates vary across foam formulations and room conditions (temperature, airflow). Speculation
Citations
- Beckett EM, et al. (2022). Evaluation of volatile organic compound (VOC) emissions from memory foam mattresses and potential implications for consumer health risk. Chemosphere. PMID 35588879 Peer-reviewed
- IARC. Methyl chloride (chloromethane) — Group 3 (not classifiable as to carcinogenicity to humans). Peer-reviewed
- ATSDR. Toxicological Profile for Chloromethane. Regulatory
Frequently asked questions
Is chloromethane part of the new-mattress smell?
Yes. In a 2022 study of memory-foam mattresses, chloromethane (methyl chloride) was one of four compounds — with 2-propanol, acetone, and toluene — that together made up roughly 81–95% of the mattress's total VOC output in the first year. It is one of the dominant emitted compounds.
Why does chloromethane matter more than the other foam VOCs?
Because it lingers. While 2-propanol and acetone fade within hours, the same study measured chloromethane's emission half-life at roughly 24 days — comparable to toluene. So chloromethane is the part of the new-foam smell that persists for weeks rather than clearing in a day. That makes ventilation over the first few weeks the sensible response.
Is chloromethane dangerous at these levels?
The bedroom levels are low. IARC classifies chloromethane as Group 3 — not classifiable as to carcinogenicity to humans. The memory-foam study concluded the measured total and individual VOC concentrations were below available health benchmarks. Chloromethane affects the central nervous system at high occupational concentrations, but new-foam levels are far below those.
Doesn't chloromethane occur naturally too?
Yes — chloromethane is the most abundant halogen-containing organic compound in the atmosphere, produced naturally by oceans, biomass burning, and vegetation. So there is always a background level in outdoor and indoor air. The new-foam contribution adds to that background temporarily, then decays over a few weeks.
Related compounds
Embr is a sleep environment company researching and addressing the chemistry of the bedroom. Research and product development in progress.
Last reviewed 2026-06-27. If you find a factual error, contact us.