In the forefront of this picture you can see a compressor that is used with tools that are placed inside the airducts to losen the dirt that is caked on to the bottom and sides of your ducts. While the General is drawing the air through the system, long lengths of hose with 360 degree high velocity nozzels are "snaked" through the entire system. This will dislodge and push any debris that might be stuck to the interior surfaces. The debris can then travel down the ducts to the General which removes it from the system. We use special spinning brushes for flex duct.

So we have the General pulling the dirt and air out while we losen the dirt inside your system. Often times this dirt is as thick as a few inches.  Here is a picture of an airduct before cleaning.