We have central air conditioning and heating which requires a duct system to deliver the cool or warm air to all the rooms. Our duct work is in the crawl space underneath the floors.

I have noticed that our home is very dusty compared to when we lived in the tropics and had no furnace at all and used window units for air conditioning (no duct work system, like we have now). I've decided that all the dust that accumulates all over everything in the house is coming from the duct system itself. My theory is that dust gets recycled back through the centralized furnace and air conditioner and recirculated back through the duct system and right back into the house again via the floor registers.

We've had our system inspected -- no leaks or anything and we use good filters at the fresh air return intake in the hallway. I thought filters were supposed to trap the dust and keep it from getting into the system. But apparently not. I wipe away the dust but after about a week my desk and everything has a thin layer of dust on it.

Does anyone else have a similar problem with dust?

Does it do any good to have the ducts professionally cleaned?