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CHEMINFO Record Number: 345
CCOHS Chemical Name: Methyl ethyl ketone peroxide

2-Butanone peroxide
Ethyl methyl ketone peroxide
MEK peroxide
Methyl ethyl ketone hydroperoxide
Peroxyde de methylethylcetone

Chemical Name French: Peroxyde de méthyl éthyl cétone
Chemical Name Spanish: Peróxido de metiletilcetona

Trade Name(s):
Butanox LPT
FR 222
Hi-Point 180
Permek N

CAS Registry Number: 1338-23-4
RTECS Number(s): EL9480000 EL9470000 EL9450000
EU EINECS/ELINCS Number: 215-661-2
Chemical Family: Organic peroxide / ketone peroxide / alkanone peroxide
Molecular Formula: C8-H16-O4


Appearance and Odour:
Colourless liquid with a characteristic odour.

Odour Threshold:
Not available

Warning Properties:
Information not available for evaluation

Commercially available as a mixture of approximately 60% MEKP and 40% diluent to reduce its sensitivity to shock. Diluents may be any combination of dimethyl phthalate, cyclohexanone peroxide or diallyl phthalate. Consult your manufacturer/supplier or Material Safety Data Sheet (MSDS) for complete information on the composition and hazards of the product you are using.

Uses and Occurrences:
Used as a polymerization catalyst in the manufacture of polyester and acrylic resins. Used as a hardening agent for fiberglass reinforced plastics.


Colourless liquid with a characteristic odour. Extreme risk of explosion by shock, friction, flame or other sources of ignition for pure peroxide. OXIDIZER. DANGEROUSLY REACTIVE. May decompose violently. Commercial products, which contain diluents, can form explosive mixtures at, or above, 52-93 deg C. Contact with water or moist air liberates irritating gases. Contents may develop pressure if exposed to water. VERY TOXIC. May be fatal if inhaled, absorbed through the skin or swallowed. CORROSIVE to the eyes, skin and respiratory tract. May cause lung injury--effects may be delayed.


Effects of Short-Term (Acute) Exposure

Inhalation of mist or vapour can cause irritation of the nose, sore throat, coughing, shortness of breath and difficulty breathing. In extreme cases, life threatening accumulation of fluid in the lungs (pulmonary edema) may occur. The symptoms of pulmonary edema often do not occur until a few hours have passed, and they are aggravated by physical effort. In some cases, pulmonary edema may be delayed in onset up to 24-72 hours after exposure.

Skin Contact:
MEKP is corrosive. Direct contact with concentrated solutions will cause irritation, redness, pain and blistering. Permanent scarring may result.
MEKP can be absorbed by skin, which can cause certain blood disorders such as hemolytic anemia.(9)

Eye Contact:
Corrosive. Direct contact will cause irritation, redness, pain and blurred vision. Blindness or other permanent damage may result.

Corrosive. Ingested MEKP can burn the lips, tongue, mouth, throat, esophagus (tube leading to the stomach) and the stomach. Abdominal pain, vomiting and diarrhea can occur. Permanent damage may result. Liver and kidney injury may occur. In extreme cases, death may result.
A man who accidentally ingested a solution of MEKP in dimethyl phthalate died. Symptoms included cardiac arrest, abdominal burns, severe metabolic acidosis, rapid liver failure, muscle disintegration and respiratory insufficiency. Death occurred after 4 days from hepatic coma (coma accompanying advance liver disease).(9)
Ingestion is not a typical route of occupational exposure.

Effects of Long-Term (Chronic) Exposure

Repeated skin contact may cause dermatitis (redness, itching, thickening, scaling of skin).

No other health effects have been reported from long-term exposure to MEKP.


No human information. Animal studies are inconclusive.

The International Agency for Research on Cancer (IARC) has not evaluated the carcinogenicity of this chemical.

The American Conference of Governmental Industrial Hygienists (ACGIH) has not assigned a carcinogenicity designation to this chemical.

The US National Toxicology Program (NTP) has not listed this chemical in its report on carcinogens.

Teratogenicity and Embryotoxicity:
No information available.

Reproductive Toxicity:
Information not available

No information available.

Toxicologically Synergistic Materials:
Information not available

Potential for Accumulation:
Probably does not accumulate. Very reactive with human tissues.


Remove source of contamination or move victim to fresh air. If breathing is difficult, oxygen may be beneficial if administered by a person trained in its use, preferably on a doctor's advice. Obtain medical attention immediately. NOTE: Symptoms of pulmonary edema may not become evident until several hours after exposure.

Skin Contact:
Avoid direct contact with this chemical. Wear chemical protective gloves, if necessary. As quickly as possible, flush contaminated area with lukewarm, gently flowing water for at least 20-30 minutes, by the clock. If irritation persists, repeat flushing. DO NOT INTERRUPT FLUSHING. If necessary, keep emergency vehicle waiting. Under running water, remove contaminated clothing, shoes and leather goods (e.g. watchbands, belts). Transport victim to an emergency care facility immediately. Discard contaminated clothing, shoes and leather goods.

Eye Contact:
Avoid direct contact. Wear chemical protective gloves, if necessary. Immediately flush the contaminated eye(s) with lukewarm, gently flowing water for at least 20-30 minutes, by the clock, while holding the eyelid(s) open. Neutral saline solution may be used as soon as it is available. DO NOT INTERRUPT FLUSHING. If necessary, keep emergency vehicle waiting. Take care not to rinse contaminated water into the unaffected eye or onto the face. If irritation persists, repeat flushing. Quickly transport victim to an emergency care facility.

Never give anything by mouth if victim is rapidly losing consciousness, is unconscious or convulsing. Have victim rinse mouth thoroughly with water. DO NOT INDUCE VOMITING. Have victim drink 240 to 300 mL (8 to 10 oz.) of water to dilute material in stomach. If milk is available, it may be administered AFTER the water is given. If vomiting occurs naturally, rinse mouth and repeat administration of water. Quickly transport victim to an emergency care facility.

First Aid Comments:
Provide general supportive measures (comfort, warmth, rest). Consult a doctor and/or the nearest Poison Control Centre for all exposures except minor instances of inhalation or skin contact.
Some recommendations in the above sections may be considered medical acts in some jurisdictions. These recommendations should be reviewed with a doctor and appropriate delegation of authority obtained, as required.
All first aid procedures should be periodically reviewed by a doctor familiar with the material and its conditions of use in the workplace.


Flash Point:
None available for pure material. 52-93 deg C (125-200 deg F) (micro open cup) (methyl ethyl ketone peroxide (MEKP) diluted with 40% dimethyl phthalate or other diluents).(5,9) MEKP is commonly sold diluted. The flash point will vary according to the diluent used and its concentration. Consult the manufacturer.

Lower Flammable (Explosive) Limit (LFL/LEL):
No information

Upper Flammable (Explosive) Limit (UFL/UEL):
No information

Autoignition (Ignition) Temperature:
Explosive decomposition occurs at 109 deg C (230 deg F). (MEKP diluted with 40% dimethyl phthalate).(9)

Sensitivity to Mechanical Impact:
Pure MEKP is sensitive to mechanical shock.(5,9)

Sensitivity to Static Charge:
Information not available

Combustion and Thermal Decomposition Products:

Fire Hazard Summary:
Dangerously reactive material. Pure MEKP is sensitive to mechanical or localized thermal shock. May decompose explosively from friction or contamination. Readily capable of detonation, or explosive decomposition, or explosive reaction. Container may explode in heat of fire. May be a combustible liquid. Commercial products, which contain diluents, can form explosive mixtures at, or above 52-93 deg C. During a fire, irritating toxic gases may be generated.

Extinguishing Media:
Small fires: Dry chemical powder, carbon dioxide, water spray or foam. Large fires: Flood fire area with water. MEKP is generally available in a diluent. Use extinguishers suitable for the diluent.

Fire Fighting Instructions:
Use extreme caution since explosive decomposition may occur under fire conditions and heat may rupture containers. Fight fire from a protected, explosion-resistant location or maximum possible distance. Approach fire from upwind to avoid hazardous vapours and toxic decomposition products.
If fire occurs in the vicinity of MEKP, use unmanned monitors and hoseholders to keep cooling streams of water on fire-exposed tanks or containers until well after the fire is out. Use flooding quantities of water. Always stay away from ends of tanks. Withdraw immediately in case of rising sound from venting safety device or any discolouration of tank due to fire.
In an advanced or massive fire, the area should be evacuated; use unmanned hoseholders or monitor nozzles. If this is is not possible, withdraw from fire area and do not attempt to fight the fire.
If a leak or spill has not ignited, use water spray to cool and disperse the vapours. Water spray may also be used to dilute spills to nonflammable mixtures and to flush spills away from ignition sources. Solid streams of water may be ineffective and spread material.
Tanks or drums should not be approached after they have been involved in a fire or heated by exposure, until they have completely cooled down. Clean-up or salvage operations should not be attempted until the MEKP is cooled. After the fire has been extinguished, explosive atmospheres may remain. Before entering area, especially confined spaces, check the atmosphere with an appropriate monitoring device.

Protection of Fire Fighters:
MEKP is very hazardous to health (inhalation and skin absorption/corrosion hazard). Do not enter without wearing specialized protective equipment suitable for the situation. Firefighter's normal protective clothing (Bunker Gear) will not provide adequate protection. A full-body encapsulating chemical protective suit with positive pressure self-contained breathing apparatus (NIOSH approved or equivalent) may be necessary.


NFPA - Comments:
NFPA has no listing for this chemical in Codes 49 or 325.


Molecular Weight: 176.22

Conversion Factor:
1 ppm = 7.2 mg/m3; 1 mg/m3 = 0.14 ppm at 25 deg C (calculated)

Physical State: Liquid
Melting Point: Not available
Boiling Point: 118 deg C (244 deg F) (decomposes) (5)
Relative Density (Specific Gravity): 1.12 at 15 deg C (water = 1) (5)
Solubility in Water: Soluble (5)
Solubility in Other Liquids: Very soluble in phthalate esters.
Coefficient of Oil/Water Distribution (Partition Coefficient): Log P(oct) = 0.914 (estimated) (9)
pH Value: Not available
Vapour Density: 6.1 (air = 1)
Vapour Pressure: Not available
Saturation Vapour Concentration: Not available
Evaporation Rate: Not available
Critical Temperature: Not applicable


Unstable. Decomposition can be initiated by heat, sunlight, friction, mechanical shock or contamination. Commercial products are normally stabilized with a diluent such as dimethyl phthalate.

Hazardous Polymerization:
Does not occur

Incompatibility - Materials to Avoid:

NOTE: Chemical reactions that could result in a hazardous situation (e.g. generation of flammable or toxic chemicals, fire or detonation) are listed here. Many of these reactions can be done safely if specific control measures (e.g. cooling of the reaction) are in place. Although not intended to be complete, an overview of important reactions involving common chemicals is provided to assist in the development of safe work practices.

Highly reactive. Vigorous decomposition can be stimulated by even trace amounts of a wide variety of contaminants, such as strong acids, bases, metals, alloys, metal salts, sulfur compounds, accelerators, reducing agents and acetone.

Hazardous Decomposition Products:

Conditions to Avoid:
Mechanical shock, friction, heat, sunlight.

Corrosivity to Metals:
Corrosive to copper, brass, mild steel and aluminum alloys.


NOTE: There is no specific information available for pure MEKP.

LC50 (rat): 200 ppm (4-hour exposure) (60% MEKP, 40% dimethyl phthalate)(1)
LC50 (mouse): 170 ppm (4-hour exposure) (60% MEKP, 40% dimethyl phthalate) (1)

LD50 (oral, rat): 484 mg/kg (60% MEKP, 40% dimethyl phthalate) (1)
LD50 (oral, mouse): 470 mg/kg (probably 60% MEKP, 40% dimethyl phthalate) (7, unconfirmed)

Eye Irritation:

At a concentration of 3% in dimethyl phthalate, MEKP caused severe irritation in rabbits (scored 57/110). The maximum non-irritating concentration was 0.6% in dimethyl phthalate. The dimethyl phthalate did not contribute significantly to the observed effects.(1)

Skin Irritation:

When applied to shaved skin, methyl ethyl ketone peroxide (MEKP) diluted with 40% dimethyl phthalate caused redness, swelling and blisters in rabbits within 2 or 3 days. The maximum non-irritating concentration was 1.5%.(1)

Effects of Long-Term (Chronic) Exposure:

Rats were given oral doses of MEKP (97 mg/kg) (60% MEKP with 40% dimethyl phthalate) 3 times weekly for 7 weeks. All 5 rats tested died.(1)

In one study, MEKP (50% solution in dibutyl phthalate) was applied twice weekly for 25 weeks to the skin of twenty mice; no tumours occurred. When a second group of mice was treated for 4 weeks with ultraviolet radiation, a few tumours occurred. Mice treated with UV radiation and then treated as above with MEKP had more tumours. It appears that MEKP was not carcinogenic, but may have had weak "promoting" activity.(4) Mice given a total dose of 7 mg MEKP (route not specified) developed a few tumours, the first of which appeared after 15 months.(8) This study provides very few experimental details. Therefore, no conclusions can be drawn about the possible carcinogenicity of MEKP.


Selected Bibliography:
(1) Floyd, E.P., et al. Toxicity studies of certain organic peroxides and hydroperoxides. Industrial Hygiene Journal. Vol. 19 (June 1958). p. 205-212
(2) Forsberg, K., et al. Quick selection guide to chemical protective clothing. 4th ed. Van Nostrand Reinhold, 2002
(3) Methyl ethyl ketone peroxide. Dangerous Properties of Industrial Materials Report. Vol. 5, no. 4 (July/Aug. 1985). p. 50-55
(4) Logani, M.K., et al. Skin-tumour promoting activity of methyl ethyl ketone peroxide--a potent lipid-peroxidizing agent. Ed. Chem. Toxic. Vol. 22, no. 11 (1984). p. 879-882
(5) Compendium of safety data sheets for research and industrial chemicals. Part I. VCH Publishers, 1985. p. 228-229
(6) Encyclopaedia of occupational health and safety. 3rd rev. ed. Vol. 2. International Labour Organization, 1983. p. 1611-1614
(7) Toxicity in plastic manufacture. Journal of the American Medical Association. Vol. 165, no. 2 (Sept. 14, 1957). p. 201-202
(8) Kotin, Paul, et al. Organic peroxides, hydrogen peroxide, epoxides, and neoplasia. Radiation Research Supplement. Vol. 3 (1963). p. 193-211
(9) HSDB record for 2-butanone peroxide. Last revision date: 92/01/28
(10) NIOSH pocket guide to chemical hazards. NIOSH, June 1994. p. 208-209
(11) Sigma-Aldrich Canada Ltd. URL:
(12) Occupational Safety and Health Administration (OSHA). Methyl Ethyl Ketone Peroxide. In: OSHA Analytical Methods Manual. Revision Date: Oct. 31, 2001. Available at: <>
(13) National Institute for Occupational Safety and Health (NIOSH). Methyl Ethyl Ketone Peroxide. In: NIOSH Manual of Analytical Methods (NMAM(R)). 4th ed. Edited by M.E. Cassinelli, et al. DHHS (NIOSH) Publication 94-113. Aug. 1994. Available at: <>

Information on chemicals reviewed in the CHEMINFO database is drawn from a number of publicly available sources. A list of general references used to compile CHEMINFO records is available in the database Help.

Review/Preparation Date: 1995-11-06

Revision Indicators:
Sampling 1996-01-01
EU class 1996-01-01
US transport 1998-03-01
Resistance of materials 1998-06-01
Bibliography 1998-06-01
UN/NA No 2002-12-18
TDG 2002-12-18
First aid skin 2003-05-16
Personal hygiene 2003-05-26
WHMIS detailed classification 2003-10-06
WHMIS proposed classification 2003-10-06
Flash point 2003-10-06
Fire hazard summary 2003-10-06
Emergency overview 2003-10-06
Short-term skin contact 2003-10-06
Handling 2003-10-06
Extinguishing media 2003-10-08
Fire fighting instructions 2003-10-08
Protection of fire fighters 2003-10-08
PEL-C final 2003-11-11
PEL-TWA transitional 2003-11-11
Bibliography 2005-03-16
Passive Sampling Devices 2005-03-16
Sampling/analysis 2005-03-16

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