# NIOSH Pocket Guide to Chemical Hazards
Methacrylic acid | CAS 79-41-4
CH2=C(CH3)COOH | RTECS OZ2975000
Synonyms & Trade Names Methacrylic acid (glacial), Methacrylic acid (inhibited), alpha-Methacrylic acid, 2-Methylacrylic acid, 2-Methylpropenoic acid | DOT ID & Guide 2531 153P (inhibited)
Exposure Limits | NIOSH REL: TWA 20 ppm (70 mg/m3) [skin]
OSHA PEL†: none
IDLH N.D. | Conversion 1 ppm = 3.52 mg/m3
Physical Description Colorless liquid or solid (below 61°F) with an acrid, repulsive odor.
MW: 86.1 | BP: 325°F | FRZ: 61°F | Sol(77°F): 9%
VP: 0.7 mmHg | IP: ? |  | Sp.Gr: 1.02 (Liquid)
Fl.P(oc): 171°F | UEL: ? | LEL: ? |
Class IIIA Combustible Liquid: Fl.P. at or above 140°F and below 200°F.
Incompatibilities & Reactivities Oxidizers, elevated temperatures, hydrochloric acid [Note: Typically contains 100 ppm of the monomethyl ether of hydroquinone to prevent polymerization.]
Measurement Methods OSHA PV2005
Personal Protection & Sanitation Skin: Prevent skin contact Eyes: Prevent eye contact Wash skin: When contaminated Remove: When wet or contaminated Change: Daily Provide: Eyewash, Quick drench | First Aid (See procedures) Eye: Irrigate immediately Skin: Water flush immediately Breathing: Respiratory support Swallow: Medical attention immediately
Respirator Recommendations To be added later
Exposure Routes inhalation, skin absorption, ingestion, skin and/or eye contact
Symptoms Irritation eyes, skin, mucous membrane; eye, skin burns
Target Organs Eyes, skin, respiratory system
See also: INTRODUCTION