The nose and the eyes can start telling you that something is not right. Testing by professionals is a sure way of knowing if you suspect you have mold and cannot see it.
Molds reproduce by means of tiny spores; the spores are invisible to the naked eye and float through outdoor and indoor air. Mold may begin growing indoors when mold spores land on surfaces that are wet. There are many types of mold, and none of them will grow without water or moisture.