Importantly, ketene is not the only aerosol toxicant whose formation under realistic vaping power settings has been questioned. For example, findings showing that e-cigarette flavorant additives were linked to elevated toxic aldehyde emissions were initially criticized by industry supporters as faulty. This judgment was based on speculation that the researchers did not account for dry puffs and overheated e-liquid. Dry puff was later discounted as relevant to aldehyde production from flavorant molecules. It was also shown that, at least in the case of one specific additive (triacetin), that acrolein, acetaldehyde and formaldehyde formation was promoted by the catalytic reaction of flavorant-derived acetic acid with e-liquid solvent. An alternative to dry puff as an explanation for enhanced levels of aerosol toxicants is film boiling. Film boiling occurs when the heat transfer between submerged metal heating coils and e-liquid is inhibited by formation of an insulating thin vapor film. The film forms due to excess heat flux at temperatures above the e-liquid boiling point, thereby promoting toxicant formation from overheated e-liquid. Significantly, e-cigarette manufacturers' recommended device power levels were shown to afford heat fluxes at levels that can produce film boiling. Film boiling thus can potentially explain why recommended safe power settings can lead to elevated aerosol toxicant emissions.In the studies described herein, a dab platform was used in conjunction with programmed temperatures and a quartz surface. There were no solvent or wicking effects involved as when using e-cigarettes, thus reducing the likelihood dry puff or film boiling as causes of ketene production. Another potential explanation for ketene as well as other toxicant emissions at relatively low temperatures is catalysis. For example, in 2018, Saliba et al. showed that toxic aldehydes, including methyl glyoxal, formaldehyde, and acetaldehyde, can form from the breakdown of the e-cigarette solvent propylene glycol at temperatures as low as ~ 80 ⁰C due to surface catalysis by metal heating element material (e.g., kanthal or nichrome). To investigate catalysis and ketene formation, a preliminary analysis of used cannabinoid EVALI patient vape cartridge components by Wu and O'Shea uncovered features including nickel and chromium filaments within a charred, oil-soaked, silica ceramic. Catalysis could have potentially occurred via the filaments, although charring is evidence of elevated temperatures. To the best of our knowledge, quartz (as used herein) has also not (to date) been identified as a heating component involved in catalysis during vaping.