During a 55-days of evaluating 11 masks for the effectiveness of filtering out PM2.5 and PM10 from the ambient air, the findings indicated the fabric masks which is populous on Hanoi street is the least effective to remove the PMs, ranging from 8-14%, the surgical masks have moderate effectiveness from 29-39%. The masks marketed for protecting health against PMs is hit and miss which one type can remove 37-52% and the other barely shows the difference. Brand-name masks such as 3M show the highest removal rate ranging from 47% to 62%, and AQBlue is from 83% to 87%. Additional analysis on 4 types indicated that fabric mask is porous and the headloss is marginal. A correlation of airflow to removal efficiency from -0.76 to -0.89 suggested a lower RE to a higher flow rate. The correlation co-efficiency of -0.51 for 3M Aura indicated improvements to allow a higher airflow without significantly reduced RE of the 3M mask. The form fitting is not evaluated in this experiment. In addition, this experiment filtered air in the 10th floor with light traffic on the ground only represents an approximate condition on the street.