E-liquids are composed primarily of propylene glycol, glycerin, nicotine and flavorings with ester flavorants becoming of recent interest. Modeling studies have suggested that under extreme operating conditions, certain ester compounds have the potential to undergo thermal degradation to produce toxic, ketene gas. This toxicant has been linked to e-cigarette or vaping use-associated lung injury (EVALI), first reported in 2019 and later attributed to thermal breakdown of the phenolic ester, vitamin E acetate. This work sought to determine if this degradation pathway was possible and under what conditions it would occur. E-liquid samples were prepared containing a single ester flavoring ingredient and vaped under moderate-to-extreme experimental conditions (0.15–1.6 Ω coils, 50–150 W power setting; 55/5/30 puff regime; puff to dryness). The generated aerosol was bubbled through an impinger containing a 4-bromobenzylamine trapping agent. Concentrated extracts were analyzed using positive ESI-LCMS. Potential ketene products were identified using the unique isotopic pattern afforded by the bromine atom. The expected masses were observed in collections where the e-liquids contained either ethyl acetate or ethyl butyrate. Additional peaks with the bromine isotopic signature were observed in the ethyl butyrate sample with the initial hypothesis being these products were the result of the fragmentation and rearrangement of the butyryl group. Further experiments have provided evidence that these and additional degradation products observed may be generated from propylene glycol and glycerol, thereby increasing the complexity of the analysis. In conclusion, sample collection under dry puffing conditions can result in the generation of numerous reactive species that readily react with our amine-based trapping agent and may include ketenes. Under non-dry puffing conditions, these species did not appear to form.