# NIOSH Pocket Guide to Chemical Hazards
Acetic anhydride | CAS 108-24-7
(CH3CO)2O | RTECS AK1925000
Synonyms & Trade Names Acetic acid anhydride, Acetic oxide, Acetyl oxide, Ethanoic anhydride | DOT ID & Guide 1715 137
Exposure Limits | NIOSH REL: C 5 ppm (20 mg/m3)
OSHA PEL†: TWA 5 ppm (20 mg/m3)
IDLH 200 ppm | Conversion 1 ppm = 4.18 mg/m3
Physical Description Colorless liquid with a strong, pungent, vinegar-like odor.
MW: 102.1 | BP: 282°F | FRZ: -99°F | Sol: 12%
VP: 4 mmHg | IP: 10.00 eV |  | Sp.Gr: 1.08
Fl.P: 120°F | UEL: 10.3% | LEL: 2.7% |
Class II Combustible Liquid: Fl.P. at or above 100°F and below 140°F.
Incompatibilities & Reactivities Water, alcohols, strong oxidizers (especially chromic acid), amines, strong caustics [Note: Corrosive to iron, steel & other metals. Reacts with water to form acetic acid.]
Measurement Methods NIOSH 3506; OSHA 82, 102
Personal Protection & Sanitation Skin: Prevent skin contact Eyes: Prevent eye contact Wash skin: When contaminated Remove: When wet or contaminated 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 125 ppm: (APF = 25) Any supplied-air respirator operated in a continuous-flow mode£/(APF = 25) Any powered, air-purifying respirator with organic vapor cartridge(s)£ Up to 200 ppm: (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 = 50) Any powered, air-purifying respirator with a tight-fitting facepiece and 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 Conjunctivitis, lacrimation (discharge of tears), corneal edema, opacity, photophobia (abnormal visual intolerance to light); nasal, pharyngeal irritation; cough, dyspnea (breathing difficulty), bronchitis; skin burns, vesiculation, sensitization dermatitis
Target Organs Eyes, skin, respiratory system
See also: INTRODUCTION