# NIOSH Pocket Guide to Chemical Hazards
Nitric acid | CAS 7697-37-2
HNO3 | RTECS QU5775000
Synonyms & Trade Names Aqua fortis, Engravers acid, Hydrogen nitrate, Red fuming nitric acid (RFNA), White fuming nitric acid (WFNA) | DOT ID & Guide 1760 154 (</=40% acid) 2031 157 (>40% acid) 2032 157 (fuming)
Exposure Limits | NIOSH REL: TWA 2 ppm (5 mg/m3) ST 4 ppm (10 mg/m3)
OSHA PEL†: TWA 2 ppm (5 mg/m3)
IDLH 25 ppm | Conversion 1 ppm = 2.58 mg/m3
Physical Description Colorless, yellow, or red, fuming liquid with an acrid, suffocating odor. [Note: Often used in an aqueous solution. Fuming nitric acid is concentrated nitric acid that contains dissolved nitrogen dioxide.]
MW: 63.0 | BP: 181°F | FRZ: -44°F | Sol: Miscible
VP: 48 mmHg | IP: 11.95 eV |  | Sp.Gr(77°F): 1.50
Fl.P: NA | UEL: NA | LEL: NA |
Noncombustible Liquid, but increases the flammability of combustible materials.
Incompatibilities & Reactivities Combustible materials, metallic powders, hydrogen sulfide, carbides, alcohols [Note: Reacts with water to produce heat. Corrosive to metals.]
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: No recommendation Provide: Eyewash (pH<2.5), Quick drench (pH<2.5) | 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 ppm: (APF = 25) Any supplied-air respirator operated in a continuous-flow mode*/(APF = 50) Any chemical cartridge respirator with a full facepiece and cartridge(s) providing protection against the compound of concern¿/(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¿/(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 (gas mask) with a chin-style, front- or back-mounted canister providing protection against the compound of concern¿/Any appropriate escape-type, self-contained breathing apparatus
Exposure Routes inhalation, ingestion, skin and/or eye contact
Symptoms Irritation eyes, skin, mucous membrane; delayed pulmonary edema, pneumonitis, bronchitis; dental erosion
Target Organs Eyes, skin, respiratory system, teeth
See also: INTRODUCTION