Skip directly to search Skip directly to A to Z list Skip directly to navigation Skip directly to page options Skip directly to site content

Methyl mercaptan

Synonyms & Trade Names
Mercaptomethane, Methanethiol, Methyl sulfhydrate
CAS No.
74-93-1
RTECS No.
PB4375000
DOT ID & Guide
1064 117
Formula
CH₃SH
Conversion
1 ppm = 1.97 mg/m3
IDLH
150 ppm
See: 74931
Exposure Limits
NIOSH REL
C 0.5 ppm (1 mg/m3) [15-minute]
OSHA PEL
C 10 ppm (20 mg/m3) See Appendix G
Measurement Methods
NIOSH 2542;
OSHA 26
See: NMAM or OSHA Methods
Physical Description
Colorless gas with a disagreeable odor like garlic or rotten cabbage. [Note: A liquid below 43°F. Shipped as a liquefied compressed gas.]
Molecular Weight
48.1
Boiling Point
43°F
Freezing Point
-186°F
Solubility
2%
Vapor Pressure
1.7 atm
Ionization Potential
9.44 eV
Specific Gravity
0.90 (Liquid at 32°F)
Flash Point
NA (Gas) (oc) 0°F (Liquid)
Upper Exposive Limit
21.8%
Lower Explosive Limit
3.9%
Relative Gas Density
1.66
Flammable Gas
Incompatibilities & Reactivities
Strong oxidizers, bleaches, copper, aluminum, nickel-copper alloys
Exposure Routes
inhalation, skin and/or eye contact (liquid)
Symptoms
irritation eyes, skin, respiratory system; narcosis; cyanosis; convulsions; liquid: frostbite
Target Organs
Eyes, skin, respiratory system, central nervous system, blood
Personal Protection/Sanitation
(See protection codes)
Skin:Prevent skin contact (liquid)/Frostbite
Eyes:Prevent eye contact (liquid)/Frostbite
Wash skin:No recommendation
Remove:When wet (flammable)
Change:No recommendation
Provide:Eyewash (liquid), Quick drench (liquid), Frostbite wash
First Aid
(See procedures)
Eye:Irrigate immediately (liquid)/Frostbite
Skin:Water flush immediately (liquid)/Frostbite
Breathing:Respiratory support
Respirator Recommendations

NIOSH

Up to 5 ppm:
(APF = 10) Any chemical cartridge respirator with organic vapor cartridge(s)
(APF = 10) Any supplied-air respirator

Up to 12.5 ppm:
(APF = 25) Any supplied-air respirator operated in a continuous-flow mode
(APF = 25) Any powered, air-purifying respirator with organic vapor cartridge(s)

Up to 25 ppm:
(APF = 50) Any chemical cartridge respirator with a full facepiece and organic vapor cartridge(s)
(APF = 50) Any air-purifying, full-facepiece respirator (gas mask) with a chin-style, front- or back-mounted organic vapor canister
(APF = 50) Any powered, air-purifying respirator with a tight-fitting facepiece and organic vapor cartridge(s)
(APF = 50) Any supplied-air respirator that has a tight-fitting facepiece and is operated in a continuous-flow mode
(APF = 50) Any self-contained breathing apparatus with a full facepiece
(APF = 50) Any supplied-air respirator with a full facepiece

Up to 150 ppm:
(APF = 1000) Any supplied-air respirator operated in a pressure-demand or other positive-pressure mode

Emergency or planned entry into unknown concentrations or IDLH conditions:
(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:
(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

Important additional information about respirator selection

See also
INTRODUCTION   ICSC CARD: 0299   MEDICAL TESTS: 0144

Follow NIOSH

NIOSH Homepage

TOP