Maybe your version of livable dirty means if you have to dust you will simply die. Dust comes from everywhere. Also, it is difficult to eliminate completely. Thick layers of dust could be a sign that it is time to change a dirty furnace or air conditioner filter. Vacuum cleaners give off excess dust, too. There are GREEN alternatives to a dusty, loud vacuum cleaner. Sanding in your living room produces dust, too. Dust can also be introduced into your home through air leaks in ducts, or air infiltration through leaky doors and windows. A deep cough might not be distracting to everybody.