I am glad I tried the allergen defense. we have pets and also the house is old. it is a filter that definitely captures the dust and helps clean the air for us. I change it as often as recommended and you can see the change of color showing how well it has worked.
These filters work well for my forced air furnace, and I also have used them to reduce the airborne dust in a room. The 20" x 20" size fits over the front side of a box fan and the filter, together with the electrostatic feature captures dust from the air.
I keep buying this particular model to substantially reduce the amount of particles of any kind floating in the air .. Also dust on the furnitures are reduced greatly with this filter in place and regularly replaced.