Unfortunately, there are a number of companies who don't perform duct cleaning correctly. These companies are scamming you out of your hard-earned money.
1. An A/C and duct hygiene inspection is needed to provide a proper proposal. Beware of low price quotes given over the phone, as "bait and switch" pricing is common by South Florida companies.
2. If a company is using a Rotobrush "Duct Cleaning" system, which is basically a large brush with a vacuum attached to it, the ducts will not be properly cleaned because there is no "negative pressure" or vacuum on the duct system. Negative pressure is required in accordance with National Air Duct Cleaners Association (NADCA) standards. The Rotobrush system pushes dirt from one duct to another since the system is never under vacuum. Read more about that here.
3. A High-Efficiency Air Filtration (HEPA) should be connected to the duct system to create negative pressure, all vents should be removed and foam should be placed in each vent to ensure complete vacuum. Next, agitation tools including brushes and air whips should be placed inside the ductwork to push the dirt towards the HEPA vacuum. Finally, an EPA approved sanitizing and deodorizing agent should be applied through each vent to ensure any mold or bacteria in the air is removed.
4. If the air handler components including the coil, blower wheel, and cabinet lining are not properly cleaned, the ducts can get re-contaminated. The blower wheel must always be removed and taken apart to be properly cleaned.
5. If Mold Resistant Duct Coating isn't applied to the fiberglass portions of your duct system after cleaning, you could have loose fiberglass in the air after cleaning, which can cause skin irritation and breathing issues.
6. We also provide and install our DuctMasters Ultraviolet Light System, which goes into the cleaned system to minimize the chance of future mold or microbial growth and has a two-year warranty on the bulb and a lifetime warranty on the ballast.
Check out the video of the DuctMasters Duct Cleanning Process: