You may not notice the buildup of dirt on your bookshelves and fixtures until it becomes significant. This can vary from region to region, and the level of dust accumulation in homes can even vary dramatically within a neighborhood. One of the most significant factors contributing to the gathering of dust in your home is the air sealing of the structure. Tightly sealed homes may resist the influx of dirt more effectively. However, breaches in your ducts can provide a source of entry for such materials in spite of careful attention to windows, doors and other exterior sources for air leaks.