It's all about the $$$$$ Been working in the plumbing trade for 30+ years. Worked in crawl spaces that looked like a nuclear disaster. Never got more than a headache. If you really want to kill mold... We use liquid chlorine in a pump up spray can like exterminators use. Just make sure the premises is vacated for at least 3 days after spraying and wear the appropriate masks while applicating. Never had a call back.