The acceleration of industrialization worsening indoor environments of industrial buildings has drawn more attention in recent years. Natural ventilation can improve indoor air quality (IAQ) and reduce carbon emissions. To evaluate gaseous pollutant levels in industrial buildings for the development of buoyancy-driven natural ventilation, two theoretical models of pollutant flushing (Model I and Model II) are developed based on the existing thermal stratification theory in combination with the mixing characteristics of lower pollutant. The results show that indoor pollutant flushing is mainly dependent on the pollution source intensity and effective ventilation area. The mixing characteristics of lower pollutant has an important effect on pollutant stratification and evolution during ventilation, but it does not change the prediction results at steady state. When the dimensionless pollution source intensity is larger than 1, the pollution source should be cleaned up or other ventilation methods should be used instead to improve IAQ. In addition, the comparisons between Model I and Model II on instantaneous pollutant concentration are significantly influenced by the pollution source intensity, and the actual pollutant concentration is more likely to be between the predicted values of Model I and Model II. To reduce pollutant concentration to a required level, the pollution source intensity should be in a certain range. The theoretical models as well as the necessary conditions for ventilation effectiveness obtained can be used for the ventilation optimization design of industrial buildings.

近年来，工业化进程的加速，工业建筑室内环境的恶化日益引起人们的关注。自然通风可以改善室内空气质量（IAQ）并减少碳排放。为了评价工业建筑内气态污染物水平，以发展浮力驱动自然通风，在现有热分层理论的基础上，结合低层污染物的混合特性，建立了两种污染物冲刷理论模型（模型一和模型二）。结果表明，室内污染物冲刷主要取决于污染源强度和有效通风面积。下层污染物的混合特性对通风过程中污染物的分层和演化有重要影响，但不改变稳态时的预测结果。当无量纲污染源强度大于1时，应清理污染源或改用其他通风方式，改善IAQ。另外，模型一与模型二瞬时污染物浓度的比较受污染源强度影响较大，实际污染物浓度更有可能介于模型一与模型二的预测值之间。要将污染物浓度降低到规定的水平，污染源强度应控制在一定范围内。获得的理论模型以及通风有效性的必要条件可用于工业建筑的通风优化设计。