Talk dirty chat line
They're usually put above the a-coil to deter bacteria on the coil but they kill everything air born as well. Sometimes you'll just get a thin residue of drywall dust, spilled drinks, food, normal dust, rotted mice, spider webs, etc... The fogging should have contained it but, it sounds like it might just be residual bacteria that the fogging didn't contain for whatever reason.Whatever the case, UV lights would definitely cut down on the smell and prevent further problems in your coil.He doesn't think the remaining drywall dust that was sprayed and incapsulated should be the source either.The only recommendation at this point is an expensive HEPA filtration system.
We have had UV lights above the coil for several years.Have been dealing with layers of odor from HVAC system for the last 3-4 months.When we started up A/C in May it had a dirty maple-brown sugar smell.We would like to find the cause and not spend lots of money on a band aid that may not work. Id call the duct cleaning company back and have them clean the duct again!
They should have cleaned the duct and the AHU the first time.They inspected most of the flex with a camera also, and saw nothing.They inspected the rest of the return duct system with camera and could find nothing either, other than the company we hired to clean the ducts left more drywall dust than they should have.Duct cleaning company believed it was a defective A/C coil and came back out the following Tuesday and replaced it. Still had an off smell from A/C however, especially when it would kick off.