# NIOSH Pocket Guide to Chemical Hazards
Methyl acetate | CAS 79-20-9
CH3COOCH3 | RTECS AI9100000
Synonyms & Trade Names Methyl ester of acetic acid, Methyl ethanoate | DOT ID & Guide 1231 129
Exposure Limits | NIOSH REL: TWA 200 ppm (610 mg/m3) ST 250 ppm (760 mg/m3)
OSHA PEL†: TWA 200 ppm (610 mg/m3)
IDLH 3100 ppm [10%LEL] | Conversion 1 ppm = 3.03 mg/m3
Physical Description Colorless liquid with a fragrant, fruity odor.
MW: 74.1 | BP: 135°F | FRZ: -145°F | Sol: 25%
VP: 173 mmHg | IP: 10.27 eV |  | Sp.Gr: 0.93
Fl.P: 14°F | UEL: 16% | LEL: 3.1% |
Class IB Flammable Liquid: Fl.P. below 73°F and BP at or above 100°F.
Incompatibilities & Reactivities Nitrates; strong oxidizers, alkalis & acids; water [Note: Reacts slowly with water to form acetic acid & methanol.]
Measurement Methods NIOSH 1458; OSHA 7 See: NMAM or OSHA Methods
Personal Protection & Sanitation Skin: Prevent skin contact Eyes: Prevent eye contact Wash skin: When contaminated Remove: When wet (flammable) Change: No recommendation | First Aid (See procedures) Eye: Irrigate immediately Skin: Water flush promptly Breathing: Respiratory support Swallow: Medical attention immediately
Respirator Recommendations NIOSH/OSHA Up to 2000 ppm: (APF = 10) Any chemical cartridge respirator with organic vapor cartridge(s)*/(APF = 10) Any supplied-air respirator* Up to 3100 ppm: (APF = 25) Any supplied-air respirator operated in a continuous-flow mode*/(APF = 50) Any chemical cartridge respirator with a full facepiece and organic vapor cartridge(s)/(APF = 50) Any air-purifying, full-facepiece respirator (gas mask) with a chin-style, front- or back-mounted organic vapor canister/(APF = 25) Any powered, air-purifying respirator with organic vapor cartridge(s)*/(APF = 50) Any self-contained breathing apparatus with a full facepiece/(APF = 50) Any supplied-air respirator with a full facepiece 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, ingestion, skin and/or eye contact
Symptoms Irritation eyes, skin, nose, throat; headache, drowsiness; optic nerve atrophy; chest tightness; in animals: narcosis
Target Organs Eyes, skin, respiratory system, central nervous system
See also: INTRODUCTION