Long humid summers, one of the heaviest pollen seasons in the country, and homes built tight enough to hold everything in. Metro Atlanta is close to a worst case for indoor air quality, and most people spend the overwhelming majority of their time indoors. Mechanical cleaning removes accumulated debris, which is the biggest single improvement available. But humidity-driven microbial growth on coils and duct surfaces needs treatment, not just extraction — and the standard one-inch filter in most homes captures very little of what actually irritates people. We'll tell you plainly which of these is worth your money for your house. Sometimes the answer is just a better filter and a duct cleaning.