Air filtration masks (referred to herein as “filter masks”) are widely used to protect people from air borne contaminants and gasses. For example, air borne dust particles are a known hazard commonly on work sites. Consequently, workers normally wear filter masks to avoid inhaling the dust particles. To that end, filter masks used in this application are manufactured with a filter material specified to prevent, among other things, a substantial majority of dust particles from being inhaled by the worker.
In addition to primarily filtering inhaled air, some filter masks are specifically manufactured to filter both inhaled and exhaled air. For example, hospital staff often wear filter masks to prevent both their germs from infecting patients, and patients' germs from infecting them.
There is a need in the art to improve the filtration efficiency of filter masks. Accordingly, filter masks with a higher efficiency filter layer and/or multiple filter layers have been developed for that purpose. However, this often has the undesirable effect of increasing the air resistance through the filter mask and may cause several problems.
For example, a person wearing the filter mask may have a more difficult time breathing due to the increased air resistance. To overcome this problem while still providing improved filtration efficiency, filter masks have been developed that have an increased filter area. Manufacture of such filter masks, however, can be quite complex. For example, increasing the filter area can cause various portions of the filter layer to overlap or can be costly to construct. Overlap can effectively increase the thickness of the filter layer, thus causing the same air resistance problem as discussed above.
Additionally, since a person wearing the mask while performing manual labor must typically breathe heavier, the filter layer(s) is more likely to flex and eventually collapse around the face. This collapse may cause portions of the face mask to contact and irritate the face of the person wearing the face mask, as well as cause discomfort. Consequently, efforts have been made to stiffen the mask, such as by adding additional material to the filter mask. However, adding additional material to the face mask adds complexity to the production process and increases cost.