Below is a list of HEPA Air Filters manufacturers from Portland, Oregon. HEPA air filters, or “high efficiency particulate air” filters are among the most effective type of air cleaner filter used, removing a minimum of 99.97 percent of unwanted particulates from an air stream, as defined by the Institute of Environmental Science. Small particles such as dust, pollen, animal dander, airborne bacterial organisms and contaminants can be removed using HEPA filters.