We have a house that is only 10 years old, and have no visible signs of water damage or leaks that may result in mold in the most obvious places. Still, my wife and kids have a cornucopia of symptoms that correlate with a mold problem.
I did the take home mold test, and there was very little activity in the petri dish in the first 72 hours, but after a week it came to life. I have been very disappointed in the lack of visual reference material that would help someone identify black mold visually in the coltroled petri dish environment.
If anyone has an expertise in this please check out this photo of our sample.