# NIOSH Pocket Guide to Chemical Hazards
Osmium tetroxide | CAS 20816-12-0
OsO4 | RTECS RN1140000
Synonyms & Trade Names Osmic acid anhydride, Osmium oxide | DOT ID & Guide 2471 154
Exposure Limits | NIOSH REL: TWA 0.002 mg/m3 (0.0002 ppm) ST 0.006 mg/m3 (0.0006 ppm)
OSHA PEL†: TWA 0.002 mg/m3
IDLH 1 mg/m3 | Conversion 1 ppm = 10.40 mg/m3
Physical Description Colorless, crystalline solid or pale-yellow mass with an unpleasant, acrid, chlorine-like odor. [Note: A liquid above 105°F.]
MW: 254.2 | BP: 266°F | MLT: 105°F | Sol(77°F): 6%
VP: 7 mmHg | IP: 12.60 eV |  | Sp.Gr: 5.10
Fl.P: NA | UEL: NA | LEL: NA |
Noncombustible Solid
Incompatibilities & Reactivities Hydrochloric acid, easily oxidized organic materials [Note: Begins to sublime below BP. Contact with other materials may cause fire.]
Measurement Methods None available
Personal Protection & Sanitation Skin: Prevent skin contact Eyes: Prevent eye contact Wash skin: When contaminated Remove: When wet or contaminated Change: Daily Provide: Eyewash | First Aid (See procedures) Eye: Irrigate immediately Skin: Soap wash immediately Breathing: Respiratory support Swallow: Medical attention immediately
Respirator Recommendations NIOSH/OSHA Up to 0.1 mg/m3: (APF = 50) Any chemical cartridge respirator with a full facepiece and cartridge(s) providing protection against the compound of concern and having a high-efficiency particulate filter/(APF = 50) Any air-purifying, full-facepiece respirator (gas mask) with a chin-style, front- or back-mounted canister providing protection against the compound of concern and having a high-efficiency particulate filter/(APF = 50) Any self-contained breathing apparatus with a full facepiece/(APF = 50) Any supplied-air respirator with a full facepiece Up to 1 mg/m3: (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 canister providing protection against the compound of concern and having a high-efficiency particulate filter/Any appropriate escape-type, self-contained breathing apparatus
Exposure Routes inhalation, ingestion, skin and/or eye contact
Symptoms Irritation eyes, respiratory system; lacrimation (discharge of tears), visual disturbance; conjunctivitis; headache; cough, dyspnea (breathing difficulty); dermatitis
Target Organs Eyes, skin, respiratory system
See also: INTRODUCTION