I own a small mechanical company. My main work is service and system replacements. I have never been a believer in duct cleaning. The company I worked for before had our duct man come out and do my house. I saw no difference. Preventive maintance is what I recomend. Remove fan and clean, seal fan compartment to prevent dust from being pulled in, filters I install media filters, they are 5″ thick and pleated. I have tested them to make sure static presure was not a issue. Heat exchangers and AC coils need to be cleaned. I will tell you this to do a good cleaning I usually spent 1-2 hrs, When I’m finished I would not have a problem eating my diner on the system. Good filters, clean system and properly tuned up are my recomdation to anyone. I’ve included my email feel free to contact me with any questions. email@example.com
If you suspect a mold problem — either because of visible growth or a musty smell consistently coming from supply vents — cleaning ducts won’t do much good if it doesn’t eliminate the mold. Mold begins with a moisture problem, and the ducts themselves are unlikely to be the source. The most likely culprits are the cooling system’s evaporator coils, which your heating and air-conditioning contractor — and most duct-cleaning companies — can inspect and maintain. Leaky return ducts can also introduce moisture. Again, if you suspect a mold problem, consider having a service company inspect the duct system for leaks.
You should be aware that although a substance may look like mold, a positive determination of whether it is mold or not can be made only by an expert and may require laboratory analysis for final confirmation. For about $50, some microbiology laboratories can tell you whether a sample sent to them on a clear strip of sticky household tape is mold or simply a substance that resembles it.