NIOSH Pocket Guide to Chemical Hazards

Methyl bromide

CAS 74-83-9


RTECS PA4900000
Synonyms & Trade Names
Bromomethane, Monobromomethane
DOT ID & Guide
1062 123


NIOSH REL: Ca See Appendix A
OSHA PEL†: C 20 ppm (80 mg/m3) [skin]
IDLH Ca [250 ppm] See: 74839 Conversion 1 ppm = 3.89 mg/m3
Physical Description
Colorless gas with a chloroform-like odor at high concentrations. [Note: A liquid below 38°F. Shipped as a liquefied compressed gas.]
MW: 95.0
BP: 38°F
FRZ: -137°F
Sol: 2%
VP: 1.9 atm
IP: 10.54 eV
RGasD: 3.36
Sp.Gr: 1.73 (Liquid at 32°F)
Fl.P: NA (Gas)
UEL: 16.0%
LEL: 10%

Flammable Gas, but only in presence of a high energy ignition source.
Incompatibilities & Reactivities
Aluminum, magnesium, strong oxidizers [Note: Attacks aluminum to form aluminum trimethyl, which is SPONTANEOUSLY flammable.]
Measurement Methods
NIOSH 2520; OSHA PV2040
See: NMAM or OSHA Methods
Personal Protection & Sanitation (See protection)
Skin: Prevent skin contact (liquid)
Eyes: Prevent eye contact (liquid)
Wash skin: When contaminated (liquid)
Remove: When wet (flammable)
Change: No recommendation
Provide: Quick drench (liquid)
First Aid (See procedures)
Eye: Irrigate immediately (liquid)
Skin: Water flush immediately (liquid)
Breathing: Respiratory support

Important additional information about respirator selection
Respirator Recommendations NIOSH
At concentrations above the NIOSH REL, or where there is no REL, at any detectable concentration:
(APF = 10,000) Any self-contained breathing apparatus that has a full facepiece and is operated in a pressure-demand or other positive-pressure mode
(APF = 10,000) Any supplied-air respirator that has a full facepiece and is operated in a pressure-demand or other positive-pressure mode in combination with an auxiliary self-contained positive-pressure breathing apparatus
(APF = 50) Any air-purifying, full-facepiece respirator (gas mask) with a chin-style, front- or back-mounted organic vapor canister/Any appropriate escape-type, self-contained breathing apparatus
Exposure Routes inhalation, skin absorption (liquid), skin and/or eye contact (liquid)
Symptoms Irritation eyes, skin, respiratory system; muscle weakness, incoordination, visual disturbance, dizziness; nausea, vomiting, headache; malaise (vague feeling of discomfort); hand tremor; convulsions; dyspnea (breathing difficulty); skin vesiculation; liquid: frostbite; [potential occupational carcinogen]
Target Organs Eyes, skin, respiratory system, central nervous system

Cancer Site [in animals: lung, kidney & forestomach tumors]
See also: INTRODUCTION   See ICSC CARD: 0109   See MEDICAL TESTS: 0138