Vent filters are inexpensive filtering kits that cover the incoming air vent. They are not as effective as a true HEPA air purifier, but they are a great start! Vent filters minimize airborne allergens entering the bedroom and other areas of the house via the ductwork. I highly recommended that vent filters be used in addition to a HEPA air purifier. It is especially important that filters cover the vents in the bedroom of the family member with allergies or asthma.