Adding Air filters

Our house is over a hundred and even how much you clean everyday. There's always dust everywhere in the house. I ask my hubby why our house like this and he said, because of the age of the house. He decide to have Sears hook up our air filterspurifier to clean the air inside the house. We use to get sick a lot during winter few years ago, but eversince we have air filters purifier and humidifier hook up. Our inside the house is not dusty and dry anymore because of the circulation of the air is clean. We had this for almost 4 years now and it's great to have in the house specially when your house is old.