Furnace cleaning is  more important than duct cleaning. This should be done by certified technicians only. Every bit of dust in your duct work has passed through your furnace. It has a huge impact on the overall health of the air in your home. Dust mites live in the dust in your furnace and multiply. Every time your blower (fan) comes up to speed, it throws dust mites, dander, dust, etc. through your duct system and into the air of your home.  The overall performance and efficiency of your furnace is greatly reduced when it's dirty. Not to mention, the life span of your furnace is reduced. Extremely dirty furnaces pose a fire hazard. After we clean your furnace we check the heat exchanger and do a carbon monoxide test to ensure your safety.