We noticed the dust floating in the air one morning, that we just happened to be in the basement at the exact time sun shine comes in the window. It was creepy, how much dust was floating round..,.
So we hung a 18" fan from the ceiling joist, strapped a medium Demo Air Net filter to the discharge end of the fan. Plugged into the pull chain light, so it's running when the light is on. That was a month ago.