Yes. Large amounts of any type of Mold in your home or office can be harmful to your health and make your family sick.
Yes if you are sick or have an immune suppressed system, the risk is much greater.
Yes some are Allergenic some are Toxic and some are Pathogenic.
Possibly, if you have some unexplained symptoms mentioned above and you do not see any visible mold/fungi Air Sampling may help yo determine what is in the air your breathing at the testing site.