# NIOSH Pocket Guide to Chemical Hazards
Trimethyl phosphite | CAS 121-45-9
(CH3O)3P | RTECS TH1400000
Synonyms & Trade Names Methyl phosphite, Trimethoxyphosphine, Trimethyl ester of phosphorous acid | DOT ID & Guide 2329 129
Exposure Limits | NIOSH REL: TWA 2 ppm (10 mg/m3)
OSHA PEL†: none
IDLH N.D. | Conversion 1 ppm = 5.08 mg/m3
Physical Description Colorless liquid with a distinctive, pungent odor.
MW: 124.1 | BP: 232°F | FRZ: -108°F | Sol: Reacts
VP(77°F): 24 mmHg | IP: ? |  | Sp.Gr: 1.05
Fl.P: 82°F | UEL: ? | LEL: ? |
Class IC Flammable Liquid: Fl.P. at or above 73°F and below 100°F.
Incompatibilities & Reactivities Magnesium perchlorate, water [Note: Reacts (hydrolyzes) with water.]
Measurement Methods None available
Personal Protection & Sanitation Skin: Prevent skin contact Eyes: Prevent eye contact Wash skin: When contaminated Remove: When wet (flammable) Change: No recommendation Provide: Quick drench | First Aid (See procedures) Eye: Irrigate immediately Skin: Soap flush immediately Breathing: Respiratory support Swallow: Medical attention immediately
Respirator Recommendations To be added later
Exposure Routes inhalation, ingestion, skin and/or eye contact
Symptoms Irritation eyes, skin, upper respiratory system; dermatitis; in animals: teratogenic effects
Target Organs Eyes, skin, respiratory system, reproductive system
See also: INTRODUCTION