It’s 11 years plus in the industry I have only had to sanitize two systems both were slab systems that were in concrete and could be cleaned with a different method than normal duct cleaning. We were able to use water to rinse out the disinfectant. Would you use a chemical on anything else you use to eat or drink with and not rinse it off? The ducts in your home should be thought of as your homes heart and lungs and breathe the same air that you do. And just like us we wouldn’t use bad chemicals in our lungs and heart.
They arrived within the time range I was given, and they even called about 20-30 minutes before arrival, so that was appreciated. They arrived and started bringing some equipment - A shop vac (yea, like you can buy at any hardware store), a handheld vacuum cleaner, and large vacuum that came in on wheels. After showing them the locations of all of the vents in the home and cold air returns, the technician (Simon) started going over a few things with me about their plan for cleaning and showing me the dust & dog hair build up in one of the vents. After showing me that, he started to try to up-sell me on additional services. That additional service was to insert a 'brush' that would agitate the dust/pet hair and allow for the vacuum to get everything out of the vents.
Pay particular attention to cooling coils, which are designed to remove water from the air and can be a major source of moisture contamination of the system that can lead to mold growth. Make sure the condensate pan drains properly. The presence of substantial standing water and/or debris indicates a problem requiring immediate attention. Check any insulation near cooling coils for wet spots.
Duct cleaning has never been shown to actually prevent health problems. Neither do studies conclusively demonstrate that particle (e.g., dust) levels in homes increase because of dirty air ducts. This is because much of the dirt in air ducts adheres to duct surfaces and does not necessarily enter the living space. It is important to keep in mind that dirty air ducts are only one of many possible sources of particles that are present in homes. Pollutants that enter the home both from outdoors and indoor activities such as cooking, cleaning, smoking, or just moving around can cause greater exposure to contaminants than dirty air ducts. Moreover, there is no evidence that a light amount of household dust or other particulate matter in air ducts poses any risk to your health.