A group of healthy adult college students fulfilling the recruitment criteria were randomly divided into two sub-groups. One sub-group weared the particulate filtering respirators for 2 continuous days during which the respirator was required to wear as much as possible both indoor and outdoor. The other group acted as normal at the same time. The measurements on health effects including heart rate varibility, blood pressure, circulating biomarkers as well as the ambient air pollution were performed in both groups during the intervention period. After a 3-week rest period,the two groups interchanged their roles of wearing the respirator or not. The same measurements of both health effects indicators and ambient air pollution were repeated.