METHYL MERCAPTAN (METHANETHIOL)†

Chemical Identification
Chemical Identification
CAS # 74-93-1
Formula

CH₄S

Synonyms
 

mercaptomethane; methanethiol; methyl sulfhydrate

Physical Properties
Physical Properties
Physical description Colorless gas with a disagreeable odor like garlic or rotten cabbage.
Boiling point 42.7°F Molecular weight 48.1
Freezing point/melting point -189.4°F Vapor pressure 1.7 atm
Flash point 0°F Vapor density 1.66
Specific gravity 0.90 at 42.8°F Ionization potential 9.44 eV
Lower explosive limit (LEL) 3.9% Upper explosive limit (UEL) 21.8%
NFPA health rating 4 NFPA fire rating 4
NFPA reactivity rating 1 NFPA special instruction
Vapor hazard ratio (VHR)
Historical exceedance percentage
Target organs
Monitoring Methods Used by OSHA
Monitoring Methods Used by OSHA
Analyte code (IMIS no.) 1643
Sampling group
Sampler/Sampling media GFF (37 mm Gelman Type A) coated with mercuric acetate [SKC 225-9007]
Sampling time*
 

100 min

Sampling volume (TWA)*
 

20 L

Sampling flow rate (TWA)*
 

0.2 L/min

Sampling volume (STEL/Peak/C)*
 

 

Sampling flow rate (STEL/Peak/C)*
 

 

Analytical method instruments GC-FPD
Method reference OSHA 26 (fully validated)
Notes
 

Protect samples from light until analysis.

Special requirements
 

 

* All sampling instructions above are recommended guidelines for OSHA Compliance Safety and Health Officers (CSHOs), please see the corresponding OSHA method reference for complete details.

Wipe Method
Wipe Method
Sampler/Sampling media
 

 

Bulk Method
Bulk Method
 

 

On-Site Screening Techniques
On-Site Screening Techniques
Device Detector tubes Detector tubes Detector tubes Detector tube Detector tube CMS Chip
Model/Type Dräger - Mercaptan 0.1/a, 8103281; Mercaptan 0.5/a, 6728981; Mercaptan 20/a, 8101871 Gastec 70L, 70 Gastec 71, 71H Matheson-Kitagawa 8014-164SA Matheson-Kitagawa 8014-164SH Mercaptan, 0.25-6 ppm range
Sampling information
(see manufacturer instructions)
0.1/a: 2 or 10 strokes, approx 0.1-15 ppm range, 0.5/a: 20 strokes, approx 0.2-5 ppm range, 20/a: 10 strokes, approx 5-100 ppm range. Uncertainty 16% 70L: 0.5-4 strokes. 70: 1-10 strokes, 0.2-120 ppm, 16% for 5-40 ppm, 8% for 40-120 ppm. 71: 0.5-10 strokes, 0.1-140 ppm range, uncertainty 16% for 2.5-20 ppm, 8% for 20-70 ppm. 71H: 0.5-2 strokes, 2-2700 ppm range, uncertainty 16% for 50-200 ppm, 8% for 200-1000 ppm. follow mfr instructions, approx 5-140 ppm range follow mfr instructions, approx 50-1000 ppm range
Exposure Limits
Exposure Limits
OSHA PEL
8-hour TWA
(ST) STEL
(C) Ceiling
Peak
NIOSH REL
Up to 10-hour TWA
(ST) STEL
(C) Ceiling
ACGIH TLV©
8-hour TWA
(ST) STEL
(C) Ceiling
CAL/OSHA PEL
8-hour TWA
(ST) STEL
(C) Ceiling
Peak
PEL-TWA
 

0.5 ppm (1 mg/m³) [Construction and Maritime Industries only]

REL-TWA
 

 

TLV-TWA
 

0.5 ppm [2003]

PEL-TWA
 
 

0.5 ppm (1 mg/m³)

PEL-STEL
 

 

REL-STEL
 

 

TLV-STEL
 
 

 

PEL-STEL
 
 

 

PEL-C
 

10 ppm (20 mg/m³) [General Industry only]

REL-C
 

0.5 ppm (1 mg/m³) [15 minutes]

TLV-C
 
 

 

PEL-C
 
 

 

Skin notation
 

N

Skin notation
 

N

Skin notation
 
 

N

Skin notation
 
 

N

Notes:
 

See 29 CFR 1910.1000 Table Z-1, 29 CFR 1926.55 Appendix A and 29 CFR 1915.1000 Table Z-Shipyards.

Notes:
 

 

Notes:
 
 

 

Notes:
 
 

 

Health factors:  See NIH-NLM PubChem. IDLH
 
 

150 ppm

Carcinogenic classifications: Not listed Notes:
 
 

 

AIHA emergency response planning guidelines - ERPG-1/ERPG-2/ERPG-3:
 
 

0.005 ppm/25 ppm/100 ppm

Additional Resources and Literature References
Additional Resources and Literature References

NOAA: CAMEO Chemicals - Methyl mercaptan

NIOSH: Pocket Guide to Chemical Hazards - Methyl mercaptan

Literature References

 
 
  • ACGIH: Documentation of the Threshold Limit Values (TLVs) and Biological Exposure Indices (BEIs) - Methyl mercaptan. See annual publication for most recent information.
  • (metabolism)
    Levitt, M.D., Furne, J., Springfield, J., Suarez, F. and DeMaster, E.: Detoxification of hydrogen sulfide and methanethiol in the cecal mucosa. J. Clin. Invest. 104(8): 1107-1114, 1999.
    Picton, R., Eggo, M.C., Merrill, G.A., Langman, M.J.S. and Singh, S.: Mucosal protection against sulphide: importance of the enzyme rhodanese. Gut 50(2): 201-205, 2002.
  • (fatalities)
    Litovitz, T.L., et al.: 2001 Annual Report of the American Association of Poison Control Centers Toxic Exposure Surveillance System. Am. J. Emerg. Med. 20(5): 391-452, 2002.

Last Updated Date : 01/05/2021