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.
You can stretch out the time between cleanings by installing a high-quality furnace air filter for $20 to $30 and change it every month. Some companies offer sealants and chemical biocides. However, there aren’t any chemical biocides registered with the EPA. The EPA warns that in most cases they aren’t needed nor has researched demonstrated that they’re very effective in decreasing the need for cleanings.
Your HVAC unit and air ducts deliver heated or cooled air throughout your home year-in and year-out. The air your HVAC unit produces travels through your ductwork and heats or cools your home via the air vents in each room. The dust and other particles in your home’s air are known as particulate matter, which the EPA defines as "a complex mixture of extremely small particles and liquid droplets." The EPA also notes that "particle pollution is made up of a number of components, including acids (such as nitrates and sulfates), organic chemicals, metals, and soil or dust particles." Having clean air ducts means fewer of these particles moving through your home. If you remove your furnace filter and hold it up to the light, you can probably see several hundred of these minuscule particles floating in the air.
I had researched by HVAC system and saw electronic air filters for over $1000. That was too much for me. But Simon introduced me to a product which uses ultraviolet light to further clean the air going into my home from the HVAC unit, and he gave me a discount because of the totally thorough cleaning I had purchased. This unit attaches to the duct coming after the air filter and comes with a lifetime warranty. Included in that lifetime warranty is a visit every two years to replace elements of this air cleaner, and a free air duct cleaning.
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.