Cleaning your air ducts and ventilation system connected to your heating and cooling systems is of utmost importance. According the National Air Duct Cleaners.
Association "if your ducts look dirty, they probably are, and that dirty HVAC systems should be inspected by a reputable, certified HVAC professional."
Just take a look at the registers and grills of your duct work throughout the hpuse. If dust is builtup either on or inside of the registers,