The Environmental Protection Agency (EPA) states that HEPA filters can remove up to 99 or 97% of dust, pollen, and other particles in the air with a size of 0.3 microns. This means that they can effectively take care of pet dander that floats in the air. However, allergens and irritants can also be found in other areas of your home, such as rugs, bedding, curtains, countertops, and tables. Therefore, it is important to keep these areas clean and to eliminate the source of allergens and irritants whenever possible.
For the best results, it is recommended to use an air purifier that has an activated carbon filter in combination with other filters, such as a HEPA filter. If you have a central air conditioning system, you should consult an accredited contractor about replacing the manufacturer's filter with an approved furnace filter with a minimum efficiency rating (MERV) of 11 or 12. Additionally, make sure that your air purifier has a HEPA filter to remove particles, since the carbon filter alone doesn't trap dust or pollen. To eliminate the smell of smoke, look for an air purifier that contains an activated carbon filter. The EPA also warns that the functionality of air purifiers is limited in terms of filtering gases and that filters must be replaced frequently to work optimally, usually approximately every three months.
A professional HVAC company must install a HEPA filter for the whole house and be properly sized for its air treatment unit in order to protect the life of the equipment and ensure that air passes through the HEPA filter and not around it.