Objectives: An explosion at the Buncefield fuel depot outside London occurred on 11 December 2005. We conducted a retrospective cohort study of airborne exposures and health status for workers deployed. Methods: Deployed individuals were identified through their occupational health departments. We sent a self-completion questionnaire asking about health symptoms during the burn and post-burn phases. The prevalence of health symptoms in workers was compared to symptoms in local residents not under the smoke plume. Results: Of 1949 eligible individuals, 815 returned questionnaires (response rate 44%). Respiratory protection was used by 39%. Symptoms were reported by 41% of individuals during the burn phase compared with 26% in the post-burn phase. In a final multivariable model, reporting of any symptoms was associated with deployment inside the inner fire cordon during the burn phase (OR 2.07, 95% CI 1.24 to 3.47) and wearing a face mask (OR 2.33, 95% CI 1.67 to 3.26). Compared with the general public, eye irritation (prevalence ratio (PR) 2.1, 95% CI 1.5 to 3.0), coughing (PR 1.3, 95% CI 1.0 to 1.8) and headaches (PR 1.7, 95% CI 1.2 to 2.5) were more common in workers deployed during the burn phase but not the post-burn phase. Conclusions: Increased reporting of symptoms close to the fire during the burn phase was consistent with increased exposure to products of combustion, although no major acute illness was reported. That only a minority of individuals used face masks, which were not protective for symptoms, raises questions about the availability of adequate respiratory protection for such incidents.