The dust and shavings of LPHV extractors are sucked through the impeller fan blade and then the waste falls into the lower bag, the air being exhausted through the top filter bag, collecting some of the fine dust on the way. This type of extraction shifts huge volumes of air at low pressure and they are very efficient at removing bulk waste such from Planers, Thicknessers & Wood Lathes etc, hence some people call them chip collectors. The down fall with all LPHV dust collector systems is when you reduce the intake hose from 100mm to 32mm the air flow volume is affected dramatically. The fine filtration efficiency can be improved somewhat by fitting a filter cartridge instead of the bag. This is a Hare & Forbes special-order item, available to order through Alltools Geelong (order code W329) for collection in store.