Fumigation of a laboratory-scale HVAC system with hydrogen peroxide for decontamination following a biological contamination incident

Aims: To evaluate hydrogen peroxide vapour (H2O2) for its ability to inactivate Bacillus spores within a laboratory-scale heating, ventilation and air-conditioning (HVAC) duct system. Methods and Results: Experiments were conducted in a closed-loop duct system, constructed of either internally lined or unlined galvanized metal. Bacterial spores were aerosol-deposited onto 18-mm-diameter test material coupons and strategically placed at several locations within the duct environment. Various concentrations of H2O2 and exposure times were evaluated to determine the sporicidal efficacy and minimum exposure needed for decontamination. For the unlined duct, high variability was observed in the recovery of spores between sample locations, likely due to complex, unpredictable flow patterns within the ducts. In comparison, the lined duct exhibited a significant desorption of the H2O2 following the fumigant dwell period and thus resulted in complete decontamination at all sampling locations. Conclusions: These findings suggest that decontamination of Bacillus sporecontaminated unlined HVAC ducts by hydrogen peroxide fumigation may require more stringent conditions (higher concentrations, longer dwell duration) than internally insulated ductwork. Significance and Impact of the Study: These data may help emergency responders when developing remediation plans during building decontamination