The original furnace was a coal fired “octopus” design which had no blower to circulate the air but relied upon warm air rising to distribute the heat. That also means that the system breathed air in from the basement and most of this type did not have a cold air return system. At some point (probably in the 1940’s) the system was upgraded to a forced air gas furnace. The upgrade included replacing the 12″ diameter air ducts exposed in the basement with 6″ ducts and a cold air return system of ducts from the two (only two) air returns on the first floor.
If I could rate this company a zero I would in a heartbeat. I purchased the service off of Groupon and to say that the groupon was misleading is an understatement. I was at work and my girlfriend was at the house when they got there (keep in mind it took six months for them to be able to get there because they were over booked). They tried to upcharge my girlfriend $250 immediately upon getting there. I told her to put me on the phone and spoke with the guy myself. He said that he would have the manager call me and that he would just start on the service. I received a text from my girlfriend 10 minutes later that the people had left. I never received a call from the manager. They didn't do all vents in the house. All they did was the main floor. It was a pathetic attempt to say the least. I received a call from the customer service representative that told me that the package I received was for a "Air Duct Cleaning with deodorizing treatment" and it was not a "Air Duct DEEP Cleaning with deodorizing treatment" and that is where the additional $250 was coming from. They then told me that if I wanted, they could come back out a week later and explain it to me professionally and also blamed Groupon for the posting to be misleading. The rep bragged about their ratings on review sites. I am guessing that this is taken down soon and deleted by the company. But if I can just save one person's time, money and efforts to better their home with this post I am more than happy to do it. STAY AWAY FROM THIS COMPANY, THEY ARE UNPROFESSIONAL AND WILL SCREW YOU OVER FOR THEM TO SAVE A PENNY.
All of the products discussed above are registered solely for the purpose of sanitizing the smooth surfaces of unlined (bare) sheet metal ducts. No products are currently registered as biocides for use on fiber glass duct board or fiber glass lined ducts, so it is important to determine if sections of your system contain these materials before permitting the application of any biocide.
Some research suggests that cleaning heating and cooling system components (e.g., cooling coils, fans and heat exchangers) may improve the efficiency of your system, resulting in a longer operating life, as well as some energy and maintenance cost savings. However, little evidence exists that cleaning only the ducts will improve the efficiency of the system.