# NIOSH Pocket Guide to Chemical Hazards
Hydroquinone | CAS 123-31-9
C6H4(OH)2 | RTECS MX3500000
Synonyms & Trade Names p-Benzenediol; 1,4-Benzenediol; Dihydroxybenzene; 1,4-Dihydroxybenzene; Quinol | DOT ID & Guide 2662 153
Exposure Limits | NIOSH REL: C 2 mg/m3 [15-minute]
OSHA PEL: TWA 2 mg/m3
IDLH 50 mg/m3 | Conversion
Physical Description Light-tan, light-gray, or colorless crystals.
MW: 110.1 | BP: 545°F | MLT: 338°F | Sol: 7%
VP: 0.00001 mmHg | IP: 7.95 eV |  | Sp.Gr: 1.33
Fl.P: 329°F (Molten) | UEL: ? | LEL: ? |
Combustible Solid; dust cloud may explode if ignited in an enclosed area.
Incompatibilities & Reactivities Strong oxidizers, alkalis
Measurement Methods NIOSH 5004
Personal Protection & Sanitation Skin: Prevent skin contact Eyes: Prevent eye contact Wash skin: When contaminated Remove: When wet or contaminated Change: Daily Provide: Eyewash (>7%) | First Aid (See procedures) Eye: Irrigate immediately Skin: Water flush Breathing: Respiratory support Swallow: Medical attention immediately
Respirator Recommendations NIOSH/OSHA Up to 50 mg/m3: (APF = 25) Any powered, air-purifying respirator with a dust filter£/(APF = 50) Any air-purifying, full-facepiece respirator with a high-efficiency particulate filter/(APF = 50) Any supplied-air respirator that has a tight-fitting facepiece and is operated in a continuous-flow mode£/(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: conjunctivitis; keratitis (inflammation of the cornea); central nervous system excitement; colored urine, nausea, dizziness, suffocation, rapid breathing; muscle twitching, delirium; collapse; skin irritation, sensitization, dermatitis
Target Organs Eyes, skin, respiratory system, central nervous system
See also: INTRODUCTION