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Methyl mercaptan																				Related Pages
Synonyms & Trade Names
			Mercaptomethane, Methanethiol, Methyl sulfhydrate
CAS No.
			74-93-1
	RTECS No.
			PB4375000
	DOT ID & Guide
			1064 117

FormulaCH3SH
	Conversion
			1 ppm = 1.97 mg/m3
	IDLH
			150 ppmSee: 74931

Exposure Limits
			NIOSH RELC 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 Weight48.1	
	Boiling Point43°F
	Freezing Point-186°F
	Solubility2%
	Vapor Pressure1.7 atm
	Ionization Potential9.44 eV											
Specific Gravity0.90 (Liquid at 32°F)	
	Flash PointNA (Gas) (oc) 0°F (Liquid)
	Upper Explosive Limit21.8%
	Lower Explosive Limit3.9%
	Relative Gas Density1.66
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 canisterAny appropriate escape-type, self-contained breathing apparatus
				Important additional information about respirator selection
See also
			INTRODUCTION
					  ICSC CARD: 0299
					  MEDICAL TESTS: 0144

			
							

			Page last reviewed:  October 30, 2019						Content
							source: 	National Institute for Occupational Safety and Health NIOSH Pocket Guide to Chemical Hazards
Introduction
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Appendices
A – NIOSH Potential Occupational Carcinogens
B – Thirteen OSHA-Regulated Carcinogens
C – Supplementary Exposure Limits
D – Substances with No Established RELs
E – OSHA Respirator Requirements for Selected Chemicals
F – Miscellaneous Notes
G – 1989 Air Contaminants Update Project: Exposure Limits NOT in Effect
Type C & CE – Definitions for Type C and Type CE Respirators
Personal Protection and Sanitation Codes
First Aid Procedures Follow NIOSH Facebook
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