Research on Evaluation Index of Indoor PM 2.5 Purification Effect

PM 2.5 has been associated with negative health impacts in studies performed throughout the world. Inevitably, the occupants are exposed to PM 2.5 that was brought in from the outdoor environment by ventilation airflow. Natural ventilation (NV) is commonly used in apartments. However, the purification methods and their effects were different for different NV apartments. The main evaluation indexes were indoor PM 2.5 mass concentration and I/O ratio. But some deficiencies have been found in the practical applications of the two indicators. This study analyzed the limitations of PM 2.5 concentration and I/O ratio in evaluation based on field measurement. The indoor PM 2.5 concentration was not suitable for large-scale, long-term evaluation. The I/O ratio had limitations in both the short-term and long-term evaluation process. In the short-term, it is mainly the impact of the lag effect. In the long-, it is due to the difference in the influencing factors of indoor and outdoor concentration, leading to inaccurate evaluation results of I/O ratio. To this end, this study established a new effect evaluation index--the percentage of purification time up to standard (PPTS). The new evaluation index has strong operability and advantages in practical application.