It is a mask that can replace a filter screen with bacteria detection. Users can choose different levels of filter screen to put in the mask inner and outer layer. The outer layer may use a carbon monoxide dye filter, medical filter, colloidal gold test, or N95 filter screen with electrostatic layers. The inner layer uses colloidal gold test paper that detects bacterial content. When the test paper is discolored due to use, it means that the bacteria have grown too much. You need to replace the filter screen and clean the mask. The body is a New-Polyurethane that can be reused after cleaning.