How do you know if undesirable molds are present in an area?

When somewhere covered in mold you may not even see it, but a good way to know its there is the smell, or the quality of the air. If the air feels musky and gross there could be some mold somewhere.

this age may represent the age of the earth's accretion, of core formation, or of the material from which the earth formed. this dating is based on evidence from radiometric age-dating of meteorite material and is consistent with the radiometric ages of the oldest-known terrestrial and lunar samples.