Fact #1: Mold is everywhere, no matter what you do. Bits of mold are part of the air you breathe everywhere you go.  Molds grow on plants and in soil, float off into the air and float in through your doors and windows.  You’ve been dealing with it all your life and there is usually no way (except in very special circumstances) to create a space with no mold in the air.  

Fact #2: Large areas of mold should really be dealt with by a professional. When mold areas get larger than about 10 square feet (about a square meter) or you don’t know the extent of the problem (for instance: mold can grow behind the walls) it is important to bring in a professional who is familiar with how to deal with mold properly.  This large area usually requires extra precautions when removing mold.  Much larger areas of mold can require very complicated procedures and precautions.  Even a common, usually harmless mold can be a health issue when there is a lot of it.

Fact #3: Stains and mysterious spots are not always mold. Sometimes a black, brown, grey, or white spot isn’t actually mold.  Efflorescence, for instance, is a whitish deposit, especially on concrete, that happens when water permeates the material and leaves behind a deposit of salts.  Note, however, that in this case there is water permeation, which may mean there is mold growing where you don’t see it.  Other spots can be caused by soot or soil deposits, giving a darker colour.  If you want to know what you’re looking at, you can collect samples yourselves and send them to mold laboratories that can test air samples or pieces of material and tell you whether you have mold or not.