# 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 73°F and BP at or above 100°F.
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