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Methyl Ethyl Ketoxime (MEKO)

  • Antioxidants
  • CAS 96-29-7
  • IUPAC: Butan-2-one oxime

Methyl Ethyl Ketoxime (MEKO) (CAS 96-29-7) appears in 1 of the 1,812 car-care products CarCareTruth tracks (as of June 2026). It is classified as a VOC.

At ingredient (substance) level: H302 (harmful if swallowed), H311 (harmful in contact with skin), H317 (may cause allergic skin reaction), H331 (toxic if inhaled), H351 (suspected carcinogen Cat 2), GHS05/GHS06/GHS07/GHS08 pictograms. These substance-level classifications drive significant hazard signals but are diluted to 0.1–1% at mixture level. At mixture concentration the contribution to product-level hazard is primarily through the skin sensitizer signal; product-level classification is governed by SDS §2, not ingredient-level codes.

Methyl ethyl ketoxime (MEKO, CAS 96-29-7) is an oxime compound used at low concentrations (typically 0.1–1%) in oil-modified alkyd and solvent-based coatings as an anti-skinning agent. It scavenges oxygen in the headspace of the container to prevent the alkyd resin from oxidatively curing before the product is applied.

At the substance level, MEKO carries serious hazard classifications including H317 (skin sensitizer), H351 (suspected carcinogen), and H331 (toxic if inhaled). These substance-level codes do not automatically transfer to the formulated product — the product-level SDS §2 classification governs. At 0.1–1% in a multi-solvent aerosol formulation, MEKO contributes to overall sensitization potential but is not the primary hazard driver.

Regulatory note: MEKO has been subject to ongoing regulatory review in the EU under REACH due to the H351 suspected carcinogen classification. Some formulators have begun transitioning to alternative anti-skinning agents.

Health & environment profile

VOC
yes
Prop 65 listed
no
Asthmagen
no
EPA Safer Choice
no
Aquatic toxicity
no
Biodegradable
yes
Bioaccumulative
no
Persistent
no
Ozone depleting
no
Microplastic
no
PFAS
no
Env. score
5/5
Purpose: Anti-skinning agent — prevents premature oxidative crosslinking of alkyd resin in the can during storage, keeping the product workable until applied

Common questions about Methyl Ethyl Ketoxime (MEKO)

What is Methyl Ethyl Ketoxime (MEKO) used for in car care?
Anti-skinning agent — prevents premature oxidative crosslinking of alkyd resin in the can during storage, keeping the product workable until applied
Is Methyl Ethyl Ketoxime (MEKO) a VOC?
Yes. Methyl Ethyl Ketoxime (MEKO) is classified as a volatile organic compound (VOC).
Is Methyl Ethyl Ketoxime (MEKO) on California's Proposition 65 list?
No. Methyl Ethyl Ketoxime (MEKO) is not on California's Proposition 65 list.
Is Methyl Ethyl Ketoxime (MEKO) biodegradable?
Yes. Methyl Ethyl Ketoxime (MEKO) has a confirmed biodegradable profile.

1 product contain this

Related

Health and environment notes translate the manufacturer Safety Data Sheet, the GHS classification, and authoritative regulatory listings (California Prop 65, EPA). Not medical advice. They describe the ingredient itself; whether a hazard applies to a finished product depends on its concentration and how it's used.