Diacetyl – What is it in Vaping?

Definition

Diacetyl is an organic compound (chemical formula C₄H₆O₂) that naturally forms during fermentation and gives foods like butter, cheese and some alcoholic drinks their rich, creamy flavour. In e-liquids it was historically added to create dessert, custard or buttery profiles such as vanilla custard, caramel popcorn or creamy tobacco. Although it is generally recognised as safe to eat, inhaling diacetyl has been linked to the serious lung disease bronchiolitis obliterans—nicknamed “popcorn lung”—after factory workers in microwave-popcorn plants became ill from breathing high concentrations. Because of this, reputable Australian and international manufacturers now test for, or completely avoid, diacetyl in disposable vapes, Nicotine“>freebase nicotine and nicotine-salt juices.

Technical Details

Diacetyl exists as a yellow-green liquid at room temperature, boils at 88 °C and has a strong buttery odour even at parts-per-million (ppm) levels. In e-liquid formulations it was typically used at 0.05–0.20 % by weight—tiny amounts that dramatically alter flavour. Gas-chromatography mass-spectrometry (GC-MS) testing can detect diacetyl down to 5 µg/g (micrograms per gram), and Australian/New Zealand Standard AS/NZS 60070:2020 recommends a maximum inhalation limit of 22 ppm for workplace air. Most responsible labs now issue “diacetyl-free” certificates, although trace levels (<10 ppm) can still appear from flavour precursors such as acetoin or acetyl propionyl, compounds sometimes used as substitutes but which may convert to diacetyl when heated by a dual-coil build or high-wattage DTL device.

Usage & Tips

• Check lab reports: Only buy e-liquids that publish recent GC-MS results showing “ND” (non-detect) for diacetyl; Australian vendors must provide these on request.
• Steer clear of “buttery” DIY one-shots unless the supplier explicitly states diacetyl-free; creamy flavours are the most common culprits.
• Watch for dry hits: Over-heating any e-liquid can break down acetoin into diacetyl—prime your coils, keep cotton saturated and avoid chain-vaping at extreme wattages.
• Use a DripTip“>drip tip made from heat-resistant materials (POM, resin, stainless steel) to minimise condensation build-up where trace chemicals might concentrate.
• If you value lung health over nostalgia, choose modern dessert blends that rely on butyric acid or other safer alternatives; they taste similar without the risk.

History & Context

Diacetyl entered the vaping lexicon around 2009 when early mixologists cloned “butterscotch” and “custard” flavours borrowed from the food industry. In 2014 a Harvard study found diacetyl in 39 of 51 e-liquid samples, sparking global media panic and prompting reputable brands to reformulate. Today, the Australian Therapeutic Goods Administration (TGA) does not mandate diacetyl testing for nicotine-free juices, yet most major labs self-regulate, aligning with EU TPD and US FDA best-practice to keep disposable vapes and open-system liquids virtually diacetyl-free.