When most people install high efficiency filters they still have problems with dust. The reason this happens is because of leaky ducts (air distribution..., the ducting system is what transfers the conditioned air from your air conditioner into your home. Most homes lose about 20% of air because of leaky ducts. This not only raises your utility bills it also makes the system run longer, shortening the life of your air conditioning system. This also puts your home on a vacuum, let me explain. If your losing 20% of the air into your attic your system has to get that 20% of air back. So what it does is pull air from where ever it can get it from. Mostly from cracks and crevices inside your home, where are the cracks and crevices at? They are behind your lighting, fan fixtures and electrical plug plates. These are penetrations on your walls and ceilings, what is inside those walls and ceilings? Harmful insulation, dust, dirt and unconditioned air. This is how these contaminants bypass your filter. This is what helps to trigger your asthma, allergies and hay fever. Properly sealing your ducting system will improve the quality of air you breathe inside your home and help to lower utility costs.