# NIOSH Pocket Guide to Chemical Hazards
Phosphoric acid | CAS 7664-38-2
H3PO4 | RTECS TB6300000
Synonyms & Trade Names Orthophosphoric acid, Phosphoric acid (aqueous), White phosphoric acid | DOT ID & Guide 1805 154
Exposure Limits | NIOSH REL: TWA 1 mg/m3 ST 3 mg/m3
OSHA PEL†: TWA 1 mg/m3
IDLH 1000 mg/m3 | Conversion
Physical Description Thick, colorless, odorless, crystalline solid. [Note: Often used in an aqueous solution.]
MW: 98.0 | BP: 415°F | MLT: 108°F | Sol: Miscible
VP: 0.03 mmHg | IP: ? |  | Sp.Gr(77°F): 1.87 (pure) 1.33 (50% solution)
Fl.P: NA | UEL: NA | LEL: NA |
Noncombustible Solid
Incompatibilities & Reactivities Strong caustics, most metals [Note: Readily reacts with metals to form flammable hydrogen gas. DO NOT MIX WITH SOLUTIONS CONTAINING BLEACH OR AMMONIA.]
Measurement Methods NIOSH 7903; OSHA ID165SG
Personal Protection & Sanitation Skin: Prevent skin contact Eyes: Prevent eye contact Wash skin: When contaminated Remove: When wet or contaminated Change: Daily Provide: Eyewash (>1.6%), Quick drench (>1.6%) | First Aid (See procedures) Eye: Irrigate immediately Skin: Water flush immediately Breathing: Respiratory support Swallow: Medical attention immediately
Respirator Recommendations NIOSH/OSHA Up to 25 mg/m3: (APF = 25) Any supplied-air respirator operated in a continuous-flow mode* Up to 50 mg/m3: (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 Up to 1000 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, upper respiratory system; eye, skin, burns; dermatitis
Target Organs Eyes, skin, respiratory system
See also: INTRODUCTION