1. OSHA Occupational Chemical Database
  2. METHYL ISOCYANATE
Label abbreviations descriptions

METHYL ISOCYANATE†

Chemical Identification
Chemical Identification
CAS # 624-83-9
Formula

C₂H₃NO
Synonyms

methyl ester of isocyanic acid; MIC; isocyanatomethane
Physical Properties
Physical Properties
Physical description Colorless liquid with a sharp, pungent odor.
Boiling point 102°F Molecular weight 57.05
Freezing point/melting point -112°F Vapor pressure 348 mmHg
Flash point 19°F Vapor density
Specific gravity 0.96 Ionization potential 10.67 eV
Lower explosive limit (LEL) 5.3% Upper explosive limit (UEL) 26%
NFPA health rating 4 NFPA fire rating 3
NFPA reactivity rating 2 NFPA special instruction W: Reacts violently or explosively with water.
Vapor hazard ratio (VHR)
Historical exceedance percentage
Target organs
Monitoring Methods Used by OSHA
Monitoring Methods Used by OSHA
Analyte code (IMIS no.) 1773
Sampling group
Sampler/Sampling media XAD-7 tube coated with 0.3 mg of 1-(2-pyridyl)piperazine (1-2PP) [No longer available]
Sampling time*

300 min
Sampling volume (TWA)*
 

15 L
Sampling flow rate (TWA)*
 

0.05 L/min
Sampling volume (STEL/Peak/C)*
 

 
Sampling flow rate (STEL/Peak/C)*
 

 
Analytical method instruments HPLC
Method reference OSHA 54 (fully validated)
Notes
 

This media is no longer available. OSHA staff please contact the SLTC prior to sampling at (801) 233-4900.
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 Infrared spectrophotometer Photoionization Detector (PID)
Model/Type Miran 1A & 1B
Sampling information
(see manufacturer instructions) 		0.1 ppm@4.4 µm
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
 

0.02 ppm (0.05 mg/m³)

 REL-TWA
 

0.02 ppm (0.05 mg/m³)

 TLV-TWA
 

0.02 ppm [2013]

 PEL-TWA
 

0.02 ppm (0.05 mg/m³)
PEL-STEL
 

 

 REL-STEL
 

 

 TLV-STEL
 

0.06 ppm [2013]

 PEL-STEL
 

 
PEL-C
 

 

 REL-C
 

 

 TLV-C
 

 

 PEL-C
 

 
Skin notation
 

Y

 Skin notation
 

Y

 Skin notation
 

Y

 Skin notation
 

Y
Notes:
 

See 29 CFR 1910.1000 Table Z-1.

 Notes:
 

 

 Notes:
 

dermal sensitization (DSEN)

 Notes:
 

 
Health factors:  See NIH-NLM PubChem. IDLH
 

3 ppm
Carcinogenic classifications: Not listed Notes:
 

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

0.025 ppm/0.25 ppm/1.5 ppm
Additional Resources and Literature References
Additional Resources and Literature References

NOAA: CAMEO Chemicals - Methyl isocyanate

NIOSH: Pocket Guide to Chemical Hazards - Methyl isocyanate

Literature References

 
  • ACGIH: Documentation of the Threshold Limit Values (TLVs) and Biological Exposure Indices (BEIs) - Methyl isocyanate. See annual publication for most recent information.

Last Updated Date : 01/05/2021