Predicting toxic species generation resulting from external cladding fires

A CFD method to predict the generation of toxic gases produced by burning external cladding is presented. The model and its assumption have been validated using BS 8414 experimental data for two cladding systems with different aluminium composite materials (ACM). The predicted temperatures are in good agreement with the measured data and the predicted toxic gas concentrations follow the measured trends. The model is then used to assess tenability conditions in a target flat and the lobby five floors above the fire origin, in which toxic smoke penetrates the flat via a half-open kitchen window. Only the impact of cladding materials is considered. Simulations indicate that if the target flat occupants commence their evacuation shortly after alarm activation, they are likely to be able to pass through the lobby and safely evacuate. However, if they delay their evacuation by 21 minutes, they are likely to become incapacitated due to inhalation of toxic gases. The PIR contribution to the fractional incapacitating dose (FIN) is approximately half that from ACM PE in the target flat and varies from a third to a half in the target lobby. Furthermore, the HCN contribution to the FIN is minor (less than 5%). • A method to calculate toxic gas generation from cladding fires is proposed • The model and its assumptions have been validated using BS 8414 experimental data • A high-rise cladding fire with ACM PE and PIR and an open window is simulated • Occupants 5 floors above fire origin with open windows are incapacitated in 21 min • The PIR contribution to the fractional incapacitating dose is half that of ACM PE