Identifiers for search
| Name | Methyl bromide |
| Formula | CH₃Br |
| IUPAC name | bromomethane |
| CAS number | 74-83-9 |
| EC number | 200-813-2 |
| UN number | 1062 — Methyl bromide, with not more than 2 % chloropicrin |
| Transport class (ADR/RID) | 2.3 (Toxic gases) |
| PubChem CID | 6323 |
| Synonyms | Bromomethane, Monobromomethane |
Physical & chemical properties
| Molar mass | 94.94 g/mol |
| Boiling point (1 atm) | 4 °C |
| Melting point | -93.66 °C |
| Critical temperature | 194 °C |
| Critical pressure | 52.3 bar |
| Vapour pressure | 1.89 bar at 20 °C |
| Gas density | 3.9739 kg/m³ (0 °C, 1013 mbar) |
| Relative density (air = 1) | 3.36 |
| Solubility in water | Concentration: 17,5 g/l |
| Appearance | gas liquefied under pressure, colourless, sweetish odour |
| Odour | sweetish odour |
| 1 ppm at 20 °C | 3.95 mg/m³ |
Behaviour with temperature and pressure
Boiling point 4 °C at 1 atm: a liquefied gas under its own vapour pressure in cylinders. Critical point 194 °C / 52.3 bar: below this temperature it can be stored as a liquid; cylinder pressure then equals the vapour pressure. Vapour pressure ≈ 1.89 bar at 20 °C — this is the pressure inside a cylinder or a switchgear compartment at that temperature, and it rises steeply with temperature (Clausius–Clapeyron). Relative density 3.36 (air = 1): heavier than air — accumulates in pits, cable basements and at floor level; place sensors low. Conversion at 20 °C, 1013 mbar: 1 ppm = 3.95 mg/m³; NDIR reads partial pressure, so readings scale with absolute pressure (value = reading × P/1013) and must be pressure-compensated.
// Poorly inflammable gas. Forms explosive mixtures with air., Ignition only by ignition sources of very high energy., Easily combustible in oxygen-enriched air; combustible air impurities (dust) also improve combustibility., Moderately soluble in water., Gas is heavier than air., Acute or chronic health hazards result from the substance.
Hazards & safety
NFPA 704
health · flammability · instability · special
GHS / CLP pictograms
| Hazard class | toxic + flammable; carcinogen suspect; ozone-depleting |
| GHS signal word | Danger |
| CLP classification | Flammable gases, Category 2; H221 Gases under pressure, liquefied gas; H280 Acute toxicity, Category 2, inhalation; H330 Skin irritation, Category 2; H315 Eye irritation, Category 2; H319 Specific Target Organ Toxicity (single exposure), Category 3; H335 Germ cell mutagenicity, Category 2; H341 Specific Target Organ Toxicity (repeated exposure), Category 2; H373 Hazardous to the aquatic environment, Acute Category 1; H400 Hazardous to the ozone layer, Category 1; H420 |
| Hazard statements | H221: Flammable gas. H280: Contains gas under pressure; may explode if heated. H315: Causes skin irritation. H319: Causes serious eye irritation. H330: Fatal if inhaled. H335: May cause respiratory irritation. H341: Suspected of causing genetic defects. H373: May cause damage to organs through prolonged or repeated exposure. H400: Very toxic to aquatic life. H420: Harms public health and the environment by destroying ozone in the upperatmosphere |
| Lower / upper explosion limit | 8.6 vol% / 20 vol% |
| Auto-ignition temperature | 535 °C · T1 |
| Seveso III named substance | yes |
Exposure limits
| EU indicative OELV (8 h TWA) | no EU IOELV |
| EU IOELV short-term (15 min) | — |
| Germany AGW (TRGS 900) | 1 ppm · 3.9 mg/m³ |
| Netherlands | wettelijke grenswaarde per Arboregeling bijlage XIII — SER grenswaarden database |
| NIOSH REL (USA) | Ca See Appendix A |
| OSHA PEL (USA) | C 20 ppm (80 mg/m3) [skin] See Appendix G |
| IDLH | Ca [250 ppm] |
// Limits change: always confirm the current national value before setting an alarm. Values above were read from the EU directives / GESTIS / NIOSH pages listed in Sources.
Effect on people
Neurotoxic fumigant with poor odour warning; symptoms (headache, nausea, tremor, convulsions, pulmonary oedema) may be delayed hours. Skin absorbs it. Classified as a suspected carcinogen (NIOSH Ca) and reproductive toxicant; German AGW 1 ppm.
GESTIS main toxic effects: acute:
irritative to corrosive action of liquid B. to mucous membranes and skin;
concentration dependent irritating potential of vapors, toxic and lung damaging action for high concentrations
chronic:
neurotoxic and skin damaging action
Recommended monitoring
- NDIR (3.3 µm / 7.3 µm) for fumigation and container clearance (0–100 ppm), or PID with confirmation; chronic limit 1 ppm (DE AGW) demands a low-range, drift-free channel.
- Alarm at 1 ppm (AGW) / 5 ppm; container/quarantine measurement before entry.
Climate & atmosphere
| GWP₁₀₀ — IPCC AR6 | 2.43 |
| GWP₁₀₀ — IPCC AR4 | 5 |
| GWP used in Reg. (EU) 2024/573 | not listed |
| Atmospheric lifetime | 0.8 years |
| Ozone depletion potential | — |
| Main IR absorption band (NDIR) | 3.3–3.4 µm (C–H stretch); 7.3 µm (CH₃ deformation); 10.5 µm |
| Note | Methyl bromide is a Montreal Protocol Annex E substance (ODP ≈ 0.6 per the Protocol); AR6 lists GWP100 = 2.43 (AR4: 5). |
Regulation windows
- Montreal Protocol Annex E — production/use banned in the EU (Reg. 2024/590) except quarantine/pre-shipment
- Workplace: DE AGW 1 ppm; carcinogen suspect (NIOSH Ca)
- Container fumigation clearance before entry
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Cite this page
Tremon Solutions (2026). Methyl bromide (CH₃Br) — properties, exposure limits, NDIR monitoring. Tremon gas reference. https://www.tremon.nl/gases/ch3br (accessed 2026-09-17).
BibTeX · embed card · QR
@misc{tremon_ch3br_2026,
author = {Tremon Solutions},
title = {Methyl bromide (CH3Br) — properties, exposure limits, NDIR monitoring},
howpublished = {Tremon gas reference, \url{https://www.tremon.nl/gases/ch3br}},
year = {2026},
note = {accessed 2026-09-17}
}<a href="https://www.tremon.nl/gases/ch3br"><img src="https://www.tremon.nl/assets/og/ch3br.png" alt="Methyl bromide — Tremon gas reference" width="600"></a>
Text and tables on this page: CC BY 4.0 — copy them into your report, SOP or slide with the link above. Data were read from the primary sources listed below; check the current national limit before setting an alarm.
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Other gases
https://www.tremon.nl/gases/ch3br · Tremon Solutions, Eindhoven · [email protected] · printed from the Tremon gas reference, data as of 2026-09-17 · CC BY 4.0Sources
- https://gestis-database.dguv.de/data?name=031600
- https://www.cdc.gov/niosh/npg/npgd0400.html
- https://pubchem.ncbi.nlm.nih.gov/compound/6323
- IPCC AR6 WG1 Ch.7 Supplementary Material, Table 7.SM.7 (https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_Chapter07_SM.pdf)
- IPCC AR4 WG1 Ch.2, Table 2.14 (https://www.ipcc.ch/site/assets/uploads/2018/02/ar4-wg1-chapter2-1.pdf)
- HITRAN/NIST IR band positions (approximate centre of the strongest band used for NDIR; https://hitran.org, https://webbook.nist.gov)
// Data compiled 2026-09-17 from the listed primary sources; null values were left blank rather than estimated.