The theory behind the ideal mask is to stop particles from going into your lungs. As much as it sounds simple but there is more to it, the majority of dust masks cannot make a good fit to your face; therefore, dust and particles will come through the gaps and enter your lungs. CANHEAL 808 dust mask overcame this big flaw by having a soft facepiece. The soft rubbery piece makes a great fit to your face and allows air to go through filter and blocks any particle intrusion via the surrounding area of the mask. After all, that is what a mask must do, only allow air through the filter.