Most major e-liquid brands sold today have removed diacetyl from their formulas, but “diacetyl-free” doesn’t always mean risk-free. The compound was widely phased out of vaping products after public concern over its link to serious lung disease, yet some budget or imported e-liquids still contain it, and common substitutes carry their own problems. Knowing which brands to look for, which flavors to be cautious about, and what the labels actually mean will help you make a more informed choice.
Why Diacetyl Is a Concern
Diacetyl is a chemical that gives foods a rich, buttery flavor. It’s safe to eat, but inhaling it is a different story. Workers in microwave popcorn factories who breathed in diacetyl vapors developed bronchiolitis obliterans, commonly called “popcorn lung.” It’s a rare, irreversible condition where inflammation and scarring obstruct the smallest airways in the lungs, making it progressively harder to breathe. Animal studies confirmed the mechanism: diacetyl vapors damage the cells lining the airways, triggering a fibrosis pathway that thickens and scars the bronchial walls.
When e-cigarettes became popular, some manufacturers added diacetyl to e-liquids to create dessert-style flavors. The amounts were far lower than what popcorn workers inhaled, but since vaping involves repeated, direct inhalation into the lungs, the concern was real enough to push most of the industry to reformulate.
Which Brands Have Removed Diacetyl
Several well-known e-liquid companies explicitly market their products as diacetyl-free and publish lab testing to back it up. Brands that have publicly committed to diacetyl-free formulas include Aqua, Black Note, Cosmic Fog, Halo, Naked 100, Pachamama, and VaporFi. Many of these companies also test for the two most common diacetyl substitutes (more on those below).
If you’re buying from a smaller or international brand, look for third-party lab reports, sometimes called certificates of analysis. Reputable companies post these on their websites or make them available on request. A lab report should specifically test for diacetyl (listed as 2,3-butanedione) and ideally for acetyl propionyl (2,3-pentanedione) as well. If a company claims to be diacetyl-free but offers no testing data, treat the claim with skepticism.
Flavor Profiles Most Likely to Contain Diacetyl
Diacetyl was never added to every vape flavor. It was used specifically to replicate rich, creamy, or buttery tastes. The highest-risk categories are custard, vanilla cream, butterscotch, caramel, and anything marketed as a bakery or dessert flavor. These are the profiles where manufacturers historically relied on diacetyl to get the taste right.
Fruit, menthol, and tobacco flavors are far less likely to have ever contained diacetyl, simply because a buttery note doesn’t fit those profiles. If your main goal is avoiding diacetyl and its substitutes entirely, sticking to fruit or menthol options from a reputable brand is the most straightforward approach.
The Problem With Diacetyl Substitutes
When the vaping industry moved away from diacetyl, many manufacturers replaced it with a structurally similar chemical called acetyl propionyl (2,3-pentanedione). This swap turned out to be less of an improvement than it sounds. A National Toxicology Program study found that acetyl propionyl has potency similar to diacetyl when it comes to airway damage after inhalation. In three-month animal studies, it caused adverse effects in the nose, larynx, trachea, and lungs. In mice, some of the tissue changes in the airways were considered atypical and potentially precancerous.
A second substitute, acetoin, fared much better in the same study. Rats and mice exposed to acetoin for up to three months showed no significant adverse respiratory effects. Acetoin is chemically related to diacetyl but does not appear to cause the same airway damage when inhaled. Some manufacturers have shifted to acetoin-based flavoring, though it doesn’t perfectly replicate the buttery richness of diacetyl.
This is why a label that says “diacetyl-free” can be misleading. If the company simply swapped in acetyl propionyl, the product may carry a comparable inhalation risk. The brands that offer the most transparency test for all three compounds and list the results.
How to Check an E-Liquid Before Buying
Start with the brand’s website. Look for a testing or transparency page where lab results are posted. The test should come from an independent, third-party lab rather than in-house testing. Key things to look for on a lab report:
- 2,3-butanedione (diacetyl): Should show as not detected or below the limit of quantification.
- 2,3-pentanedione (acetyl propionyl): Same standard. If this compound is present, the product hasn’t meaningfully improved on the diacetyl risk.
- Acetoin: Less concerning based on current evidence, but worth noting if listed.
If a brand doesn’t provide any lab data, check whether the product is manufactured in a country with strong consumer safety regulations. E-liquids produced in the EU must comply with the Tobacco Products Directive, which imposes ingredient disclosure requirements. Products manufactured in unregulated markets carry higher uncertainty.
Diacetyl-Free Still Means Inhaling Other Chemicals
Removing diacetyl addresses one specific risk, but e-liquids contain other flavoring chemicals, solvents like propylene glycol and vegetable glycerin, and nicotine. The long-term effects of inhaling many common flavoring compounds haven’t been fully studied. Some flavoring agents that are perfectly safe in food have never been evaluated for inhalation safety, which is a fundamentally different route of exposure.
Choosing a diacetyl-free product is a reasonable step if you vape, but it doesn’t eliminate all respiratory risk. It removes one of the few flavoring chemicals with a well-documented, specific mechanism of serious lung injury.