We will probably revisit this particular page quite a bit since it is so chock full of amazing links and info!
I suggest reading the intro on the page. The first thing it will tell you is the types of pollutants and the reasons why they exist around the house. I think the important thing to remember when reading this type of material is not to lose your head thinking you have to change immediately today. Some indicators that you should look into your home's air quality are if you are getting sick regularly, your sinuses are in overdrive, the odor of the house is stale or bad, or if you are just curious about how much better you might feel as a result!