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Chemical Sampling Information (CSI)
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General Description

Synonyms: Methanethiol

OSHA IMIS Code Number: 1643

Chemical Abstracts Service (CAS) Registry Number: 74-93-1

NIOSH Registry of Toxic Effects of Chemical Substances (RTECS) Identification Number: PB4375000

Department of Transportation Regulation Number (49 CFR 172.101) and Guide: 1064 117

NIOSH Pocket Guide to Chemical Hazards, Methyl Mercaptan: chemical description, physical properties, potentially hazardous incompatibilities, and more

Exposure Limits

OSHA Permissible Exposure Limit (PEL):

General Industry: 29 CFR 1910.1000 Table Z-1 - 10 ppm, 20 mg/m3 Ceiling

Construction Industry: 29 CFR 1926.55 Appendix A - 0.5 ppm, 1 mg/m3 TWA

Maritime: 29 CFR 1915.1000 Table Z-Shipyards - 0.5 ppm, 1 mg/m3 TWA

American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Value (TLV): 0.5 ppm, 0.98 mg/m3 TWA

National Institute for Occupational Safety and Health (NIOSH) Recommended Exposure Limit (REL): 0.5 ppm, 1 mg/m3 Ceiling (15 Minutes)

Health Factors

NIOSH Immediately Dangerous To Life or Health Concentration (IDLH): 150 ppm

Potential Symptoms: Irritation of eyes, skin, respiratory tract; cough, sore throat; headache; nausea; shortness of breath; unconsciousness; pulmonary edema (delayed); CNS effects (narcosis, cyanosis, seizures); respiratory failure; frostbite (on contact with liquid)

Health Effects: Odor (HE20); CNS effects (HE7); Irritation-Eye, Nose, Throat, Skin---Moderate (HE15); Respiratory effects---edema (HE11)

Affected Organs: Respiratory system, CNS, eyes, skin, blood

Notes:

  1. As a product of intestinal flora, methyl mercaptan is metabolized to hydrogen sulfide, which in turn, is metabolized to thiosulfate by the enzyme rhodanese.
  2. Three worker fatalties at a chemical plant accident involving methyl mercaptan were characterized by sulfhemoglobin levels of 6-15%.

Literature Basis:

  • International Chemical Safety Cards (WHO/IPCS/ILO): Methyl mercaptan.
  • (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.

Date Last Revised: 07/17/2003

Monitoring Methods used by OSHA

Primary Laboratory Sampling/Analytical Method (SLC1):

  • sampling media: Coated Glass Fiber Filter (37 mm Gelman Type A) Coating is Mercuric Acetate
    analytical solvent: (20 mL:5 mL) 25% Aqueous HCl:Methylene Chloride
    maximum volume: 20 Liters
    maximum flow rate: 0.2 L/min (TWA or Ceiling)
    current analytical method: Gas Chromatography; GC/FPD
    method reference: OSHA Manual of Analytical Methods (OSHA 26)
    method classification: Fully Validated
    note: Protect samples from light until analysis.

On-Site Sampling Techniques/Methods:

  • device: Detector Tube
    manufacturer: AUER/MSA
    model/type: Ethyl Mercaptan-0.5, MSA P/N 804589, AUER P/N 5086-815
    sampling information: follow manufacturer's instructions
    upper measurement limit: 5 ppm
    detection limit: approx. 0.5 ppm
    overall uncertainty: unknown
    method reference: on-site air secondary (manufacturer)

  • device: Detector Tube
    manufacturer: Dräger
    model/type: Mercaptan 0.1/a, order no. 81 03281
    sampling information: 2 or 10 strokes
    upper measurement limit: 15 ppm
    detection limit: approx. 0.1 ppm
    overall uncertainty: 16%
    method reference: on-site air secondary (manufacturer)

  • device: Detector Tube
    manufacturer: Dräger
    model/type: Mercaptan 0.5/a, order no. 67 28981
    sampling information: 20 strokes
    upper measurement limit: 5 ppm
    detection limit: approx. 0.2 ppm
    overall uncertainty: 16%
    method reference: on-site air secondary (manufacturer)

  • device: Detector Tube
    manufacturer: Dräger
    model/type: Mercaptan 20/a, order no. 81 01871
    sampling information: 10 strokes
    upper measurement limit: 100 ppm
    detection limit: approx. 5 ppm
    overall uncertainty: 16%
    method reference: on-site air secondary (manufacturer)

  • device: Detector Tube
    manufacturer: Gastec
    model/type: 71
    sampling information: 0.5 to 10 strokes
    upper measurement limit: 140 ppm
    detection limit: 0.1 ppm
    overall uncertainty: 16% for 2.5 to 20 ppm, 8% for 20 to 70 ppm
    method reference: on-site air secondary (manufacturer)

  • device: Detector Tube
    manufacturer: Gastec
    model/type: 71H
    sampling information: 0.5 to 2 strokes
    upper measurement limit: 2700 ppm
    detection limit: 2 ppm
    overall uncertainty: 16% for 50 to 200 ppm, 8% for 200 to 1000 ppm
    method reference: on-site air secondary (manufacturer)

  • device: Detector Tube
    manufacturer: Gastec
    model/type: 70L
    sampling information: 0.5 to 4 strokes
    upper measurement limit: 8 ppm
    detection limit: 0.05 ppm
    overall uncertainty: 16% for 0.5 to 1 ppm, 8% for 1 to 4 ppm
    method reference: on-site air secondary (manufacturer)

  • device: Detector Tube
    manufacturer: Gastec
    model/type: 70
    sampling information: 1 to 10 strokes
    upper measurement limit: 120 ppm
    detection limit: 0.2 ppm
    overall uncertainty: 16% for 5 to 40 ppm, 8% for 40 to 120 ppm
    method reference: on-site air secondary (manufacturer)

  • device: Detector Tube
    manufacturer: Matheson-Kitagawa
    model/type: 8014-164SA
    sampling information: follow manufacturer's instructions
    upper measurement limit: 140 ppm
    detection limit: approx. 5 ppm
    overall uncertainty: unknown
    method reference: on-site air secondary (manufacturer)

  • device: Detector Tube
    manufacturer: Matheson-Kitagawa
    model/type: 8014-164SH
    sampling information: follow manufacturer's instructions
    upper measurement limit: 1000 ppm
    detection limit: approx. 50 ppm
    overall uncertainty: unknown
    method reference: on-site air secondary (manufacturer)

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