Outdoor & Yard / Compounds / Carbon monoxide

Carbon monoxide in the yard and garden

High risk for your yard

Carbon monoxide is the leading cause of accidental poisoning death in the US (~400 deaths/year) and the most common cause of death from poisoning globally. Mechanism: CO binds hemoglobin with ~250× the affinity of O₂, forming carboxyhemoglobin (COHb), reducing O₂ delivery to tissues; also binds myoglobin and cytochrome c oxidase. Symptoms at COHb 10–20%: headache, dizziness, nausea; 30–40%: confusion, collapse; >50%: seizures, loss of consciousness, death. Sources: gas appliances, generators, fireplaces, vehicle exhaust in enclosed spaces, charcoal grills. OSHA PEL 50 ppm; NIOSH IDLH 1,200 ppm. CO detectors are legally required in residential units in most US states. Treatment: 100% O₂; hyperbaric O₂ for severe cases.

What is carbon monoxide?

Also known as: carbon monooxide, Carbonic oxide, Carbon oxide (CO), carbon(II) oxide.

IUPAC name
carbon monoxide
CAS number
630-08-0
Molecular formula
CO
Molecular weight
28.01 g/mol
SMILES
[C-]#[O+]
PubChem CID
281

Risk for people, pets,

High risk

Carbon monoxide is the leading cause of accidental poisoning death in the US (~400 deaths/year) and the most common cause of death from poisoning globally. Mechanism: CO binds hemoglobin with ~250× the affinity of O₂, forming carboxyhemoglobin (COHb), reducing O₂ delivery to tissues; also binds myoglobin and cytochrome c oxidase. Symptoms at COHb 10–20%: headache, dizziness, nausea; 30–40%: confusion, collapse; >50%: seizures, loss of consciousness, death. Sources: gas appliances, generators, fireplaces, vehicle exhaust in enclosed spaces, charcoal grills. OSHA PEL 50 ppm; NIOSH IDLH 1,200 ppm. CO detectors are legally required in residential units in most US states. Treatment: 100% O₂; hyperbaric O₂ for severe cases.

Regulatory consensus

4 regulatory and scientific bodies have classified Carbon monoxide. The classifications differ — that's the data.

AgencyYearClassificationNotes
OSHA—Occupational exposure limit
EPA CTX / Skin-Eye—Eye Irritation: Not classified (score: low)
EPA CTX / Skin-Eye—Skin Irritation: Not classified (score: low)
EPA CTX / Skin-Eye—Skin Sensitization: Not classified (score: low)

Regulators apply different standards of evidence — animal-data weighting, exposure-pattern assumptions, epidemiological power thresholds — which is why two scientific bodies can review the same data and reach different conclusions. The disagreement is the data.

Where your yard encounter carbon monoxide

  • Outdoor Air — Vehicle exhaust, Industrial emissions, Power plant discharge
  • Indoor Air — Combustion byproducts, Office buildings, Parking garages

Safer alternatives

Lower-risk approaches that achieve a similar outcome to Carbon monoxide:

  • Process redesign to avoid hazardous intermediates
    Trade-offs: May require significant R&D investment. Not always feasible.
    Relative cost: 1.2-2×

Frequently asked questions

Is carbon monoxide safe for your yard?

Carbon monoxide is the leading cause of accidental poisoning death in the US (~400 deaths/year) and the most common cause of death from poisoning globally. Mechanism: CO binds hemoglobin with ~250× the affinity of O₂, forming carboxyhemoglobin (COHb), reducing O₂ delivery to tissues; also binds myoglobin and cytochrome c oxidase. Symptoms at COHb 10–20%: headache, dizziness, nausea; 30–40%: confusion, collapse; >50%: seizures, loss of consciousness, death. Sources: gas appliances, generators, fireplaces, vehicle exhaust in enclosed spaces, charcoal grills. OSHA PEL 50 ppm; NIOSH IDLH 1,200 ppm. CO detectors are legally required in residential units in most US states. Treatment: 100% O₂; hyperbaric O₂ for severe cases.

What products contain carbon monoxide?

Carbon monoxide appears in: Vehicle exhaust (Outdoor air); Industrial emissions (Outdoor air); Combustion byproducts (Indoor air); Office buildings (Indoor air).

Why do regulators disagree about carbon monoxide?

Carbon monoxide has been classified by 4 agencies including OSHA, EPA CTX / Skin-Eye, EPA CTX / Skin-Eye, EPA CTX / Skin-Eye, with differing conclusions. Regulators apply different standards of evidence (animal data weighting, exposure-pattern assumptions, epidemiological power thresholds), which is why two scientific bodies can review the same data and reach different conclusions. See the regulatory consensus table on this page for the full picture.

See Carbon monoxide in the outdoor app

Look up products containing carbon monoxide, compare to alternatives, and explore the full data record.

Open in outdoor View raw API data

Sources (4)
  1. CDC: Carbon Monoxide Poisoning — Facts and Prevention (2023) — report
  2. ATSDR Toxicological Profile for Carbon Monoxide (2012) — report
  3. US EPA National Ambient Air Quality Standards for Carbon Monoxide (2011) — regulatory
  4. ASPCA Animal Poison Control Center: Carbon Monoxide Toxicosis in Companion Animals (2019) — report

Reference data, not professional advice. Aggregates publicly available regulatory and scientific data; not a substitute for veterinary, medical, legal, or regulatory advice. Why we built ALETHEIA →