Do you notice birds relaxing on your roof? If so, then you need to get your ladder out and check for nests. Bird nests that are built in the wrong spots (near soffits) can block airflow that should be moving through your home or office building. As airflow decreases, indoor air becomes more stagnant. Stagnant air can collect pollutants like carbon dioxide and VOC’s in the presence of chemicals or cleaners.
Blocked eavestroughs on the other hand will cause water backup which can result in flooding and the introduction of bacteria or mold that can become airborne once in your home. You know what happens next.