NIOSH Pocket Guide to Chemical Hazards

Formic acid

CAS 64-18-6


RTECS LQ4900000
Synonyms & Trade Names
Formic acid (85-95% in aqueous solution); Hydrogen carboxylic acid; Methanoic acid
DOT ID & Guide
1779 153


NIOSH REL: TWA 5 ppm (9 mg/m3)
OSHA PEL: TWA 5 ppm (9 mg/m3)
IDLH 30 ppm See: 64186 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
See: NMAM or OSHA Methods
Personal Protection & Sanitation (See protection)
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
Important additional information about respirator selection
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
(APF = 50) Any air-purifying, full-facepiece respirator (gas mask) with a chin-style, front- or back-mounted organic vapor canister having an N100, R100, or P100 filter. Click here for information on selection of N, R, or P filters./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   See ICSC CARD: 0485