you might need to consult a professional. My Mother is selling her town home. she had black mold in one spot the size of a silver dollar. Being the type of person she is, on the disclosure, she stated she did have black mold. She had to have it reinspected and a certificate of sorts issued to show it was gone forever on that spot.
This is in Corpus Christi which is having epidemic of black mold and the adjoining scare.