This is an actual picture inside my ductwork AFTER a scammer had cleaned! I called references and thought I was being very thorough. If it could happen to me, it can happen to anyone. I figured out the scam while they were 'working' but not before they blew contaminated dust all over my house. Know everything they will do for your and what kind of equipment they will use.
Ductwork and Hvac systems are a HUGE source of mold problems. To avoid mold, know that mold can and does grow on metal or flexible ductwork, cooling coils, condensate pans and clogged condensate drains. Check Hvac system and clean ductwork every 8 years at a minimum depending on the situation. Flexible ductwork cannot be effectively cleaned so avoid it if you can. The food source for mold is dirt and dust! So, TOXIC MOLD CAN AND DOES GROW INSIDE DUCTWORK AND HVAC SYSTEMS.
Swab testing for mold inside ductwork is a good idea. Solutions may vary depending on the mold species you find.
Click here for a Duct cleaning resources and checklist
Use only cleaning contractors certified by this organization if you can:
The NACDA is a great resource and has a contractor search engine on it's site, along with other helpful resources. (The HVAC Inspection, Maintenance and Restoration Association) The best contractors will only do duct cleaning - no carpets, no upholstery, no remediation or other work. If you can find one that hospitals also use, that is a good sign
There still may be good and bad contractors thru this organization's membership list, but at least it's a start!
For a list of my 10 Tips to know for duct cleaning CLICK HERE.