Label abbreviations descriptions

METHYL ISOCYANATE†

Chemical Identification
CAS # 624-83-9
Formula

C₂H₃NO
Synonyms

methyl ester of isocyanic acid; MIC; isocyanatomethane

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
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) 233-5100.
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 Infrared spectrophotometer Hazard Assessment Test Kit for Aliphatic Isocyanates Photoionization Detector (PID)
Model/Type Miran 1A & 1B 769-1003
Sampling information
(see manufacturer instructions) 		0.1 ppm@4.4 µm Isocyanate Surface and Dermal Sampling, Hazard Assessment Test Kit for Aliphatic Isocyanates

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

Last Updated Date : 04/02/2025