Air Purifying Respiratory Protection Mechanical filter respiratory protection devices are commonly known as dust masks. These simple filters commonly consist of a molded filter designed to cover the nose and mouth. The filter is held in place by one or two elastic straps that are stretched over the head. Some of these type masks have a valve made into the filtering substance to allow easier breathing. When the filter becomes clogged, the complete unit is discarded.
Units having two straps fit better.
Sufficient levels of oxygen must be present in the air to be filtered. Chemical Cartridge Chemical cartridge respirators provide a higher level of protection than dust masks. A full face respirator also contains a lens to cover the eyes. Replaceable cartridges containing activated carbon are used to filter the incoming air. Prefilters are usually installed on the outside of the cartridges.