Pocket filters are the most common air filters in HVAC systems for industrial and commercial applications as well as for residential use to improve indoor air quality and comfort. The filters in the supply air are used as first and second filter stages, either as complete filtration solutions for these applications or as prefilters for cleanroom process applications. The filters are also used in the exhaust air or in recirculation systems to protect the air handling units. Pocket filters have a significantly higher dust holding capacity and longer lifetimes than other filters.