At a glance
| Chemical family | A small inorganic gas — a fast-acting chemical asphyxiant. A combustion product, not a typical off-gassing VOC |
| CAS number | 74-90-8 |
| Classification | A potent acute poison that blocks cellular respiration. Not evaluated as a carcinogen by IARC, EPA or the U.S. DHHS — the danger is rapid asphyxiation, not cancer |
| Where you encounter it | Combustion of nitrogen-containing materials — polyurethane foam, wool, nylon, melamine, silk — i.e. mattresses, bedding and furnishings when they burn; also a minor component of cigarette smoke |
| Sleep micro-environment relevance | Not an emission from intact materials. The relevance is fire toxicity: the materials you sleep on become a source of a fast-acting poison in a fire |
| Activated carbon capture | Not an everyday air-quality control. The relevant protections are smoke alarms and escape planning, not air filtration |
What it is
Hydrogen cyanide is a small, colorless gas with a faint almond odor and a fearsome reputation it has earned. It is a fast-acting chemical asphyxiant: rather than displacing oxygen, it stops the body's cells from using oxygen, which is why high exposures cause collapse and death within minutes. Regulatory — ATSDR, Cyanide ToxFAQs
One thing it is not is a carcinogen. Cyanide has not been evaluated for cancer by IARC, the EPA or the U.S. Department of Health and Human Services; its hazard is acute poisoning, not the slow chronic risk that defines most of this Atlas. Regulatory — ATSDR That single fact reframes the whole page: hydrogen cyanide matters in the bedroom not as something you breathe night after night, but as something that appears suddenly, in a fire.
How it relates to the bedroom
What the foam becomes when it burns
The connection to the sleep environment is direct and physical. Polyurethane foam — the bulk of most mattresses and upholstered furniture — contains nitrogen, and when it burns it releases hydrogen cyanide along with carbon monoxide. A comprehensive review of polyurethane fire toxicity identifies carbon monoxide and hydrogen cyanide as the two major asphyxiants formed during flaming combustion of the foam, and shows that the ventilation condition is decisive: under-ventilated fires generate far higher yields of both. Peer-reviewed — McKenna & Hull 2016, Fire Science Reviews Wool, nylon and other nitrogen-containing furnishings add to the cyanide load. Inferred — any nitrogen-containing material can yield HCN on combustion
The firefighter's molecule, made literal
This is the page where my old trade and this one meet. A broad review of fire-smoke toxicity concluded that nitrogen-containing synthetic polymers release hydrogen cyanide as a major toxic threat alongside carbon monoxide, and that hydrogen cyanide is frequently found in appreciable amounts in the blood of victims of modern fires. Peer-reviewed — Alarie 2002, Critical Reviews in Toxicology The reason modern furnished rooms can become unsurvivable in minutes is precisely that the synthetic materials filling them — foam above all — produce these fast asphyxiants quickly. The smoke is not just hot and dark; it is chemically loaded. Inferred — synthesising the combined CO/HCN asphyxiant picture
The honest calibration: this is a fire question, not an air-quality one
It would be easy, and wrong, to turn this into a reason to fear your mattress on an ordinary night. Intact foam does not release meaningful hydrogen cyanide; you are not being poisoned in your sleep. Inferred — HCN is a combustion product, not an off-gassing VOC The one small everyday source is tobacco smoke, which contains hydrogen cyanide. Regulatory — ATSDR Everything else about this compound belongs to the fire scenario — which means the protective measures that matter are the ones the fire service has been preaching for decades, not anything you can filter out of the air.
What the research says
- It is a fast-acting asphyxiant, not a carcinogen. Blocks cellular oxygen use; not evaluated for cancer. Regulatory — ATSDR
- Polyurethane foam is a principal source — in a fire. CO and HCN are the two major asphyxiants from flaming foam combustion. Peer-reviewed — McKenna & Hull 2016
- It is a leading cause of fire death. Found in appreciable amounts in the blood of modern fire victims. Peer-reviewed — Alarie 2002
- Under-ventilated fires are worst. Smoldering-then-flaming conditions maximize HCN yield. Peer-reviewed — McKenna & Hull 2016
What helps reduce the risk
Working smoke alarms. The single highest-value step. Alarms in and near the bedroom buy the minutes that a fast asphyxiant does not otherwise allow. Inferred — detection time is decisive given HCN's speed
A practiced escape plan. Because hydrogen cyanide acts in minutes, getting out fast matters more than any material choice. Inferred — from HCN's rapid action
No indoor smoking. It removes the one small everyday cyanide source and eliminates a leading ignition cause at the same time. Regulatory — ATSDR
Consider the materials at the margin. The more synthetic nitrogen-containing foam concentrated in a sleeping space, the more hydrogen cyanide if it ignites — a reason flammability standards and fire-safe design exist. Peer-reviewed — McKenna & Hull 2016
What does NOT help
- Air purifiers or carbon filters. Hydrogen cyanide is a fire-event gas, not a daily indoor pollutant to be filtered out. Inferred
- Treating it as a reason to fear an intact mattress. The everyday off-gassing risk is effectively zero; the real protection is fire detection and escape. Inferred
Open research questions
- How hydrogen cyanide yields from modern mattress and bedding assemblies compare to older material mixes under realistic bedroom-fire conditions. Speculation
- The degree to which fire-retardant treatments shift, rather than reduce, the balance of carbon monoxide and hydrogen cyanide in foam smoke. Speculation
Citations
- McKenna ST, Hull TR (2016). The fire toxicity of polyurethane foams. Fire Science Reviews, 5:3. DOI 10.1186/s40038-016-0012-3 — CO and HCN identified as the two major asphyxiants of flaming PU-foam combustion; ventilation governs yield. Peer-reviewed
- Alarie Y (2002). Toxicity of fire smoke. Critical Reviews in Toxicology, 32(4):259–289. Reference record — nitrogen-containing polymers release HCN as a major fire-smoke toxicant; HCN appreciable in modern fire-victim blood. Peer-reviewed
- U.S. ATSDR. Cyanide — ToxFAQs (October 2024). Hydrogen cyanide a colorless, fast-acting poison; cigarette smoke a named exposure route; not evaluated for carcinogenicity by IARC, EPA or DHHS. atsdr.cdc.gov Regulatory
Frequently asked questions
Does my mattress give off hydrogen cyanide?
Not while it is intact. Hydrogen cyanide is not a meaningful off-gassing emission from a normal mattress — you are not breathing it from your bed at night. It is a combustion product: it is released when the nitrogen-containing materials in a mattress and bedroom, especially polyurethane foam, wool and nylon, burn. The relevance is fire safety, not everyday air quality.
Why is hydrogen cyanide important in a fire?
Because it is one of the two main asphyxiants in modern fire smoke, alongside carbon monoxide. Hydrogen cyanide is a fast-acting poison that blocks the body's cells from using oxygen, so it can incapacitate and kill quickly. Polyurethane foam — the bulk of most mattresses and upholstered furniture — produces both carbon monoxide and hydrogen cyanide when it burns, and under-ventilated, smoldering-then-flaming fires produce especially high yields. This is a large part of why modern furnished rooms can become lethal in minutes.
Is hydrogen cyanide a carcinogen?
No. Hydrogen cyanide is an acute poison, not a cancer agent; IARC, the EPA and the U.S. DHHS have not evaluated cyanide for carcinogenicity, and its danger is rapid asphyxiation rather than long-term cancer risk. This makes it different from most Atlas compounds: the concern is a fire event measured in minutes, not a chronic low-level exposure measured in years.
How do I reduce the risk in the bedroom?
Treat it as a fire-safety question, because that is what it is. Working smoke alarms in and near the bedroom buy the minutes that matter; a practiced escape plan matters more than any material choice. Not smoking indoors removes the one small everyday source of hydrogen cyanide and eliminates a common ignition source at once. Materials matter at the margin — the more synthetic nitrogen-containing foam in a room, the more hydrogen cyanide if it ignites — but detection and escape are what save lives.
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.