NIOSH Pocket Guide to Chemical Hazards

Methyl chloride

CAS 74-87-3


RTECS PA6300000
Synonyms & Trade Names
Chloromethane, Monochloromethane
DOT ID & Guide
1063 115


NIOSH REL: Ca See Appendix A
OSHA PEL†: TWA 100 ppm C 200 ppm 300 ppm (5-minute maximum peak in any 3 hours)
IDLH Ca [2000 ppm] See: 74873 Conversion 1 ppm = 2.07 mg/m3
Physical Description
Colorless gas with a faint, sweet odor which is not noticeable at dangerous concentrations. [Note: Shipped as a liquefied compressed gas.]
MW: 50.5
BP: -12°F
FRZ: -144°F
Sol: 0.5%
VP: 5.0 atm
IP: 11.28 eV
RGasD: 1.78

Fl.P: NA (Gas)
UEL: 17.4%
LEL: 8.1%

Flammable Gas
Incompatibilities & Reactivities
Chemically-active metals such as potassium, powdered aluminum, zinc & magnesium; water [Note: Reacts with water (hydrolyzes) to form hydrochloric acid.]
Measurement Methods
NIOSH 1001
See: NMAM or OSHA Methods
Personal Protection & Sanitation (See protection)
Skin: Frostbite
Eyes: Frostbite
Wash skin: No recommendation
Remove: When wet (flammable)
Change: No recommendation
Provide: Frostbite wash
First Aid (See procedures)
Eye: Frostbite
Skin: Frostbite
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
Escape: Any appropriate escape-type, self-contained breathing apparatus
Exposure Routes inhalation, skin and/or eye contact (liquid)
Symptoms Dizziness, nausea, vomiting; visual disturbance, stagger, slurred speech, convulsions, coma; liver, kidney damage; liquid: frostbite; reproductive, teratogenic effects; [potential occupational carcinogen]
Target Organs central nervous system, liver, kidneys, reproductive system

Cancer Site [in animals: lung, kidney & forestomach tumors]
See also: INTRODUCTION   See ICSC CARD: 0419   See MEDICAL TESTS: 0140