# NIOSH Pocket Guide to Chemical Hazards
Calcium oxide | CAS 1305-78-8
CaO | RTECS EW3100000
Synonyms & Trade Names Burned lime, Burnt lime, Lime, Pebble lime, Quick lime, Unslaked lime | DOT ID & Guide 1910 157
Exposure Limits | NIOSH REL: TWA 2 mg/m3
OSHA PEL: TWA 5 mg/m3
IDLH 25 mg/m3 | Conversion
Physical Description White or gray, odorless lumps or granular powder.
MW: 56.1 | BP: 5162°F | MLT: 4662°F | Sol: Reacts
VP: 0 mmHg (approx) | IP: NA |  | Sp.Gr: 3.34
Fl.P: NA | UEL: NA | LEL: NA |
Noncombustible Solid, but will support combustion by liberation of oxygen.
Incompatibilities & Reactivities Water (liberates heat), fluorine, ethanol [Note: Reacts with water to form calcium hydroxide.]
Measurement Methods NIOSH 7020; OSHA ID121
Personal Protection & Sanitation Skin: Prevent skin contact Eyes: Prevent eye contact Wash skin: When contaminated/Daily Remove: When wet or contaminated Change: Daily 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 Up to 10 mg/m3: (APF = 5) Any dust and mist respirator Up to 20 mg/m3: (APF = 10) Any dust and mist respirator except single-use and quarter-mask respirators/(APF = 10) Any supplied-air respirator Up to 25 mg/m3: (APF = 25) Any supplied-air respirator operated in a continuous-flow mode/(APF = 25) Any powered, air-purifying respirator with a high-efficiency particulate filter/(APF = 50) Any air-purifying, full-facepiece respirator with 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 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, upper respiratory tract; ulcer, perforation nasal septum; pneumonitis; dermatitis
Target Organs Eyes, skin, respiratory system
See also: INTRODUCTION