Each of the cannabinoid acetates possesses a phenyl acetate substructure. Phenyl acetate has been known since 1938 to convert to ketene and phenol under thermolytic conditions (Scheme 1). Ketene is a highly reactive poisonous gas. NIOSH has established 5 ppm as the immediately dangerous to life or health (IDLH) value for ketene. In 2019, Wu and O'Shea reported the formation of ketene from vitamin E acetate when vaping with a commercial electronic cigarette, 8 leading to ketene's consideration as a possible causative agent of e-cigarette or vaping use-associated lung injury (EVALI). Since cannabinoid acetates and vitamin E acetate both contain phenyl acetate moieties, we hypothesized that vaping cannabinoid acetates could lead to ketene exposure.