# NIOSH Pocket Guide to Chemical Hazards
Formic acid | CAS 64-18-6
HCOOH | RTECS LQ4900000
Synonyms & Trade Names Formic acid (85-95% in aqueous solution); Hydrogen carboxylic acid; Methanoic acid | DOT ID & Guide 1779 153
Exposure Limits | NIOSH REL: TWA 5 ppm (9 mg/m3)
OSHA PEL: TWA 5 ppm (9 mg/m3)
IDLH 30 ppm | Conversion 1 ppm = 1.88 mg/m3
Physical Description Colorless liquid with a pungent, penetrating odor. [Note: Often used in an aqueous solution.]
MW: 46.0 | BP: 224°F (90% solution) | FRZ: 20°F (90% solution) | Sol: Miscible
VP: 35 mmHg | IP: 11.05 eV |  | Sp.Gr: 1.22 (90% solution)
Fl.P(oc): 122°F (90% solution) | UEL: 57% (90% solution) | LEL: 18% (90% solution) |
Class II Combustible Liquid (90% solution)
Incompatibilities & Reactivities Strong oxidizers, strong caustics, concentrated sulfuric acid [Note: Corrosive to metals.]
Measurement Methods NIOSH 2011; OSHA ID186SG
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, Quick drench | First Aid (See procedures) Eye: Irrigate immediately Skin: Water flush immediately Breathing: Respiratory support Swallow: Medical attention immediately
Respirator Recommendations NIOSH/OSHA Up to 30 ppm: (APF = 10) Any supplied-air respirator*/(APF = 50) Any self-contained breathing apparatus 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 organic vapor canister having 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, throat; skin burns, dermatitis; lacrimation (discharge of tears); rhinorrhea (discharge of thin mucus); cough, dyspnea (breathing difficulty); nausea
Target Organs Eyes, skin, respiratory system
See also: INTRODUCTION