What is the best filter to purchase?

There are hundreds of filtration and air cleaning products on the market. Generally speaking, for household dust, a 1” fiberglass or pleated media filter will do just fine. If you have severe allergies, you might consider an extended like pleated media filter (MERV 11 or higher), a bypass air cleaner with a HEPA or TFP cell or an electronic air cleaner. If you are having problems with odors, a filter with carbon or zeolite might be what you need. Also, there are products that use different ionization or oxidation process that can help too.The most important thing to remember is that air conditioning and heating systems do not make dust. Before investing big money on air cleaning products, take time to find and eliminate the source of the problem by having your home and ducts tested for leakage and infiltration. You might just find out you don’t need expensive air cleaners and save energy as well.