# NIOSH Pocket Guide to Chemical Hazards
Boron oxide | CAS 1303-86-2
B2O3 | RTECS ED7900000
Synonyms & Trade Names Boric anhydride, Boric oxide, Boron trioxide | DOT ID & Guide
Exposure Limits | NIOSH REL: TWA 10 mg/m3
OSHA PEL†: TWA 15 mg/m3
IDLH 2000 mg/m3 | Conversion
Physical Description Colorless, semitransparent lumps or hard, white, odorless crystals.
MW: 69.6 | BP: 3380°F | MLT: 842°F | Sol: 3%
VP: 0 mmHg (approx) | IP: 13.50 eV |  | Sp.Gr: 2.46
Fl.P: NA | UEL: NA | LEL: NA |
Noncombustible Solid
Incompatibilities & Reactivities Water [Note: Reacts slowly with water to form boric acid.]
Measurement Methods NIOSH 0500
Personal Protection & Sanitation Skin: Prevent skin contact Eyes: Prevent eye contact Wash skin: When contaminated Remove: When wet or contaminated Change: No recommendation | First Aid (See procedures) Eye: Irrigate immediately Skin: Water flush promptly Breathing: Fresh air Swallow: Medical attention immediately
Respirator Recommendations NIOSH Up to 50 mg/m3: (APF = 5) Any dust and mist respirator* Up to 100 mg/m3: (APF = 10) Any dust and mist respirator except single-use and quarter-mask respirators^*/(APF = 10) Any supplied-air respirator* Up to 250 mg/m3: (APF = 25) Any supplied-air respirator operated in a continuous-flow mode*/(APF = 25) Any powered, air-purifying respirator with a dust and mist filter^* Up to 500 mg/m3: (APF = 50) Any air-purifying, full-facepiece respirator with a high-efficiency particulate filter/(APF = 50) Any powered, air-purifying respirator with a tight-fitting facepiece and 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 2000 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 with 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, skin, respiratory system; cough; conjunctivitis; skin erythema (skin redness)
Target Organs Eyes, skin, respiratory system
See also: INTRODUCTION