Strategy to Optimise Building Ventilation to Aid Rescue of Hostages Held by Terrorists

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Abstract
When hostages are held by terrorists in a building, one strategy to secure their release is to release an airborne anaesthetic agent through the ventilation system. There are considerable practical difficulties to this approach. In order to control the indoor environment and the anaesthetic agent through a well organised air distribution system, it is necessary first to analyse the demand (the amount of anaesthetic needed and where in the building it is required) and then to optimise the operation of the ventilation system. A scale called “population injury rate” ( PIR) is proposed to predict the acute toxic impact on a certain group of occupants in a given period of time together with the concept of “accessibility of the supplied air” ( ASA). Since, ideally, hostages and terrorists should be treated differently, ventilation delivery would be set based on a compromise between the extreme requirements for each occupant group. The model, arrived at from simplification of a real ventilation system, has been formulated as a non-linear programming problem and then solved to seek the most appropriate strategy for this kind of emergency ventilation. The results in an illustrative case show that both the ventilation objective and the solution approach are effective in theory to meet the requirements under such anti-terrorism circumstances. Some recommendations are also given on applying the model in practice.