A note about custard flavours: Acetyl propionyl and acetoin are used in the production of custard flavourings (from any vendors). These ingredients are used instead of diacetyl as they are considered safe for food flavours. It has been shown that under some circumstances these ingredients can form to ceate trace amounts of the molecule Diacetyl. Diacetyl in large amounts, when heated can be an inhalation risk, although minute their are risks with inhaling any food flavours as there have not been any long term studies regarding inhalation safety. Cigarettea however carry up to 100 times the amount of diacetyl that have been found in e-liquids.