NIOSH Pocket Guide to Chemical Hazards

Methyl ethyl ketone peroxide

CAS 1338-23-4


RTECS EL9450000
Synonyms & Trade Names
2-Butanone peroxide, Ethyl methyl ketone peroxide, MEKP, MEK peroxide, Methyl ethyl ketone hydroperoxide
DOT ID & Guide


NIOSH REL: C 0.2 ppm (1.5 mg/m3)
OSHA PEL†: none
IDLH N.D. See: IDLH INDEX Conversion 1 ppm = 7.21 mg/m3
Physical Description
Colorless liquid with a characteristic odor. [Note: Explosive decomposition occurs at 230°F.]
MW: 176.2
BP: 244°F (Decomposes)
FRZ: ?
Sol: Soluble
VP: ?
IP: ?

Sp.Gr(59°F): 1.12
Fl.P(oc): 125-200°F (60% MEKP)
UEL: ?
LEL: ?

Combustible Liquid
Incompatibilities & Reactivities
Organic materials, heat, flames, sunlight, trace contaminants [Note: A strong oxidizing agent. Pure MEKP is shock sensitive. Commercial product is diluted with 40% dimethyl phthalate, cyclohexane peroxide, or diallyl phthalate to reduce sensitivity to shock.]
Measurement Methods
NIOSH 3508; OSHA 77
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 wash immediately
Breathing: Respiratory support
Swallow: Medical attention immediately
Important additional information about respirator selection
Respirator Recommendations Not available.
Exposure Routes inhalation, ingestion, skin and/or eye contact
Symptoms Irritation eyes, skin, nose, throat; cough, dyspnea (breathing difficulty), pulmonary edema; blurred vision; blisters, scars skin; abdominal pain, vomiting, diarrhea; dermatitis; in animals: liver, kidney damage
Target Organs Eyes, skin, respiratory system, liver, kidneys