NIOSH Pocket Guide to Chemical Hazards

Methyl isocyanate CAS 624-83-9
CH3NCO RTECS NQ9450000
Synonyms & Trade Names
Methyl ester of isocyanic acid, MIC
DOT ID & Guide
2480 155
Exposure
Limits
NIOSH REL: TWA 0.02 ppm (0.05 mg/m3) [skin]
OSHA PEL: TWA 0.02 ppm (0.05 mg/m3) [skin]
IDLH 3 ppm Conversion 1 ppm = 2.34 mg/m3
Physical Description
Colorless liquid with a sharp, pungent odor.
MW: 57.1
BP: 139°F
FRZ: -49°F
Sol(59°F): 10%
VP: 348 mmHg
IP: 10.67 eV

Sp.Gr: 0.96
Fl.P: 19°F
UEL: 26%
LEL: 5.3%

Class IB Flammable Liquid: Fl.P. below 73F and BP at or above 100F.
Incompatibilities & Reactivities
Water, oxidizers, acids, alkalis, amines, iron, tin, copper [Note: Usually contains inhibitors to prevent polymerization.]
Measurement Methods
OSHA 54
Personal Protection & Sanitation
Skin: Prevent skin contact
Eyes: Prevent eye contact
Wash skin: When contaminated
Remove: When wet (flammable)
Change: No recommendation
Provide: Eyewash, Quick drench
First Aid (See procedures)
Eye: Irrigate immediately
Skin: Water flush immediately
Breathing: Respiratory support
Swallow: Medical attention immediately
Respirator Recommendations NIOSH/OSHA
Up to 0.2 ppm: (APF = 10) Any supplied-air respirator*
Up to 0.5 ppm: (APF = 25) Any supplied-air respirator operated in a continuous-flow mode*
Up to 1 ppm: (APF = 50) Any self-contained breathing apparatus with a full facepiece/(APF = 50) Any supplied-air respirator with a full facepiece
Up to 3 ppm: (APF = 2000) Any supplied-air respirator that has a full facepiece and is operated in a pressure-demand or other positive-pressure mode
Emergency or planned entry into unknown concentrations or IDLH conditions: (APF = 10,000) Any self-contained breathing apparatus that has a full facepiece and is operated in a pressure-demand or other positive-pressure mode/(APF = 10,000) Any supplied-air respirator that has a full facepiece and is operated in a pressure-demand or other positive-pressure mode in combination with an auxiliary self-contained positive-pressure breathing apparatus
Escape: (APF = 50) Any air-purifying, full-facepiece respirator (gas mask) with a chin-style, front- or back-mounted organic vapor canister/Any appropriate escape-type, self-contained breathing apparatus
Exposure Routes inhalation, skin absorption, ingestion, skin and/or eye contact
Symptoms Irritation eyes, skin, nose, throat; respiratory sensitization, cough, pulmonary secretions, chest pain, dyspnea (breathing difficulty); asthma; eye, skin damage; in animals: pulmonary edema
Target Organs Eyes, skin, respiratory system
See also: INTRODUCTION