We use all gas operated equipment and hook up our vacuum directly to the main trunk line that connects to the furnace as well as agitating all ducts under high pressure.
We do this by running air whips and air nozzles powered by a 2 stage air compressor into each duct to dislodge all dust/debris so our vaccum can pull it into the area where it is connected.
We do make access panels into the main trunk lines to be able to agitate and insert our hose from the vacuum to remove all dust/debris. All panels are plugged up and sealed upon completion.
No it will not. Our vacuum runs the entire length of the cleaning and we use vent covers to seal off all vents during the process to prevent any dust/debris from flying out.