"Indoor air quality," or IAQ, is a relatively new topic in environmental safety. While a lot of attention has been placed on outdoor pollution over the past few decades, the focus on indoor air quality is just beginning. The quality of a home's air mainly has to do with the amount of pollutants inside, but it's also determined by humidity and ventilation levels. The U.S. Environmental Protection Agency has found that concentrations of pollutants can be up to 100 times higher indoors than outdoors. The American Lung Association estimates that most people spend 90% of their time indoors, so clean indoor air is very important.