The quality of protection against PM2.5 is highly depends on how well a mask is sealing your face. Through the transparent body of Totobobo mask, you are able to determine the quality of the seal by checking the “watermark”. If necessary, you can Reshape the mask to improve the seal. Below is a short video showing how to ReShape a mask by a hair dryer.
* Alternative: ReShape Totobobo mask with Hot and Cold water