Label abbreviations descriptions

METHYL MERCAPTAN (METHANETHIOL)†

Chemical Identification
CAS # 74-93-1
Formula

CH₄S
Synonyms
 

mercaptomethane; methanethiol; methyl sulfhydrate

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
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.

Bulk/Wipe Method
Wipe Sampler/Sampling media
 

 
Bulk Method
 

 

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
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:

The OSHA PEL applies to Construction and Maritime Industries only. See 29 CFR 1910.1000 Table Z-1, 29 CFR 1926.55 Table 1 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

Last Updated Date : 06/08/2022