Label abbreviations descriptions

METHYLENE BISPHENYL ISOCYANATE (MDI; 4,4-DIPHENYLMETHANE DIISOCYANATE)†

Chemical Identification
CAS # 101-68-8
Formula
 

C₁₅H₁₀N₂O₂
Synonyms
 

4,4-diphenylmethane diisocyanate; MDI; 4,4-diisocyanadiphenyl-methane; methylenebis(4-phenylisocyanate); methylene bis(phenyl isocyanate); methylene di-p-phenylene ester of isocyanic acid

Physical Properties
Physical description White to light-yellow, odorless flakes.
Boiling point 597°F Molecular weight 250.3
Freezing point/melting point 99°F Vapor pressure 0.000005 mmHg at 77°F
Flash point 390°F Vapor density
Specific gravity 1.23 (Solid at 77°F) 1.19 (Liquid at 122°F) Ionization potential
Lower explosive limit (LEL) Upper explosive limit (UEL)
NFPA health rating 2 NFPA fire rating 1
NFPA reactivity rating 0 NFPA special instruction
Vapor hazard ratio (VHR)
Historical exceedance percentage
Target organs

Monitoring Methods Used by OSHA
Analyte code (IMIS no.) 1073
Sampling group
Sampler/Sampling media Isocyanate Sampling Filter Kit - GFF (37 mm, open-faced) coated with 1 mg 1-(2-pyridyl)piperazine [SLTC103]
Sampling time*
 

15 min
Sampling volume (TWA)*
 
 

15 L
Sampling flow rate (TWA)*
 
 

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

 
Sampling flow rate (STEL/Peak/C)*
 
 

 
Analytical method instruments UHPLC
Method reference OSHA 5002 (fully validated)
Notes
 
 

Refrigerate coated filters and protect from light until used. Sample open-faced!!
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 Hazard Assessment Test Kit for Aromatic Isocyanates
Model/Type 769-1002
Sampling information
(see manufacturer instructions) 		Isocyanate Surface and Dermal Sampling, Hazard Assessment Test Kit for Aromatic 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
 
 

 

 REL-TWA
 
 

0.005 ppm (0.05 mg/m³)

 TLV-TWA
 
 

0.005 ppm [1985]

 PEL-TWA
 
 

0.005 ppm (0.051 mg/m³)
PEL-STEL
 
 

 

 REL-STEL
 
 

 

 TLV-STEL
 
 

 

 PEL-STEL
 
 

 
PEL-C
 
 

0.02 ppm (0.2 mg/m³)

 REL-C
 
 

0.020 ppm (0.2 mg/m³) [10 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.

 Notes:
 
 

 

 Notes:
 
 

 

 Notes:
 
 

 
Health factors:  See NIH-NLM PubChem. IDLH
 
 

75 mg/m³
Carcinogenic classifications: IARC-3, EPA-CBD;D Notes:
 
 

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

--/5 mg/m³/55 mg/m³

Additional Resources and Literature References

Last Updated Date : 04/02/2025