This article was written by David McGibbon, Festool Service/Tech Support

Festool filter bags – just ordinary paper bags?

The Festool CT dust extractors filter dust in different stages. The first level of filtration is the filter bag. The filter bag has to fulfill very demanding duties: It has to hold back as much dust as possible (goal is 99.9%) and at the same time it has to let the air pass to create the suction. Also important for the bag is to make sure the dust does not clog the pores to make sure air can keep flowing through until the bag is full. The bag needs to prevent as much dust as possible from reaching the final filtration step, the main filter. The less the main filter has to filter, the longer it is going to last and the better a job it can do.

The bag has to be tear proof, needs to sit secure in the CT with secure connection between the bag and the CT, the glued joints have to last and have to be dust proof. The bag needs reinforcements at spots with high stress. At the same time the filter bag has to have an acceptable selling price.

Does all that sound like an ordinary paper bag?

Quite a demanding job! An ordinary paper bag couldn’t do it. The Festool CT filter bags are a complex system of paper layers. It took quite a while and numerous hours in the laboratory to develop the right bag for the CT. The engineers were checking how the dust flows into the bag and how a maximum of filtration can be achieved. They also have to fight with phenomena like the “dust cake”. In certain dust extractors the dust accumulates to a certain spot and creates a “dust cake”, a very hard piece of dust sitting in the dust bag opposite to the inlet, causing the bag to tear. There are countless hours that went into the design of the filter bag for a good reason: Proper dust extraction only works with the right filter bag.

What are the benefits of the filter bag?

• Main filter does not clog too fast and does not have to be replaced constantly = save money
• Easy and fast way to dump the dust = save time
• Clean way to dump the dust, no clean-up = save time
• Less dust in the air = healthier
• Better protection for the vacuum motor in case the main filter is leaking = machine lasts longer, save replacement cost