Study On Key Issues Of Emergency Ventilation To Control Indoor Contaminant Dispersion

In the emergencies of releasing toxic gas in public places, emergency ventilation system plays an important role for ensuring indoor occupants' safety. To guide the design and operation of emergency ventilation system, intensive study on several key issues of emergency ventilation theory has conducted. The main creative work and corresponding conclusions are as follows:(1) The concept of exposure cell was proposed and its layered model was established subsequently. Exposure cell and its layered model constitute the theoretical foundation for quantitative analysis of the influence of indoor contaminant on occupant in any period of time.(2) The models of short-term exposure dose in unsteady indoor micro-environment were proposed. Compared with the existing models, the accuracy has improved greatly. Based on this, the method of predicting indoor occupants' casualty rate was presented. The results can be used to guide the optimal design of emergency ventilation system and evacuation route.(3) This dissertation also proposed the new concept of efficiency factor, which provides the new perspective for evaluation of ventilation effectiveness. Two series evaluating factors, Efficiency Factor of Contaminant Source (EFCS) and Efficiency Factor of Supply air (EFSA), are proposed separately. The series indices are applicable to both unsteady and steady indoor environment and they can be used to guide decision-making of emergency ventilation and occupant evacuation.(4) The risk exist in the decision-making of emergency ventilation was pointed out definitely. The certainty of contaminant source location information was summarized as three typical cases: completely certain, incompletely certain and completely uncertain, and the corresponding decision analysis model was built as well. Due to the advantages of the above models, decision makers need only considering the possible contaminant source location but without considering the contaminant source strength and type in the state space of the decision model, which reduce the scale of the state space and simplify the decision-making process greatly.