How exactly do you expect to kill or remove mold without it ? You can’t even clean your hvac systems coils without moisture of some type ,if you use a steam cleaner you can literally clean the whole system minus the electronics . You should do more research and possibly talk to people who do the work before posting , but don’t listen to me i only have a class A contractor license ,epa license , install /repair hvacs , rent and flip houses for a living .
Most organizations concerned with duct cleaning, including EPA, NADCA, NAIMA and the Sheet Metal and Air Conditioning Contractors' National Association (SMACNA) do not currently recommend the routine use of sealants to encapsulate contaminants in any type of duct. Instances when the use of sealants to encapsulate the duct surfaces may be appropriate include the repair of damaged fiber glass insulation or when combating fire damage within ducts. Sealants should never be used on wet duct liner, to cover actively growing mold, or to cover debris in the ducts, and should only be applied after cleaning according to NADCA or other appropriate guidelines or standards.
There are many interesting comments from several informed individuals. The question that has not been answered is how do duct systems get dusty and dirty? As a RESNET Home Energy Rater, I perform pressure tests on homes and duct systems, and the one common thread is . . . most air delivery sytems have large amounts of air leakage. The solution is to seal the duct system, and pay particular attention to the return duct system and ductwork near the air handler (the 'blower'). As others have said, a captive (sealed) duct system with proper filter maintenance should be more then adequate for most occupants. For those who have allergy, asthma, or other breathing problems, a filter with a higher MERV rating (number should be listed on the package) or a HEPA filter are good choices. These filters will capture smaller particulates and should improve the indoor air quality. Again, make certain that the entire duct system is sealed, preferably with mastic, second choice UL-181 foil tape - never use cloth duct (also known as duck) tape.
HVAC equipment is estimated to last about 15 to 20 years. Yet over the years, parts go out and need to be repaired. Heat sensors, exchangers, and ducts can become worn out. Air conditioning motors may need repairing from time to time. For repairs to your heating and air conditioning systems, and even general maintenance, let HomeAdvisor help. Enter your zip code and let us connect you with prescreened HVAC repair services near you.