It's in the bag.
All Festool CT Dust Extractor models feature a self-cleaning filter bag that
solves a problem that plagues other dust extractors and vacuums. During normal use,
fine particles of dust cling to the inner lining of the filter bag resulting in
caking. This coating of dust lowers the effective suction power dramatically resulting
in poor extraction efficiency and performance. Caking can also cause additional
strain on your dust extractor's motor and contribute to premature failure.
Festool has addressed this issue by developing a unique pliable fleece filter bag.
Because the bag is not rigid like many other types of bags, such as paper bags,
it prevents caking. This means that your Festool CT Dust Extractor continues
to deliver full suction until the bag is virtually completely full. Other manufacturers'
bags do not counter this caking effect and suction is reduced dramatically throughout
the use of the bag, often resulting in a situation where suction is lost before
the bag is completely full. When this occurs, you're paying full price for a partially
The Festool filter bag also serves as a pre-filter and is able to trap dust particles
down to five millionths of a meter, or 5 microns. This is about the same size as
a red blood cell. By arresting these small particles, in addition to larger chips,
the bag extends the life of your main HEPA filter, reducing wear and tear as well
as the expense of frequent filter replacement.
Bag disposal is quick and mess-free. An integrated closure on the bag shuts the
opening to prevent spilling. The material is made to be tear resistant and prevent
bag blow outs which can be messy to clean up. Now, that's smart.
Principles of the Self-Cleaning Filter Bag
During this stage, the dust extractor has been used for a period of time. As air
is drawn in from the hose and expelled through the exhaust housing in the rear,
a layer of dust particles has begun to build up on the bag lining. This is build
up is typical in all types of vacuum and extractor bags.
In the next stage, power has been turned off. With the Festool CT units'
self-cleaning filter bag, the pliable bag material allows it to begin to collapse
when suction is removed. The bag crumples onto itself as it deflates. The crumpling
helps break up dust clinging to the bag lining.
As the dust extractor is turned back on, the bag reinflates quickly. The bag "snaps"
back into its inflated position which further breaks loose dust particles and they
fall to the bottom of the bag.
Suction efficiency as bag fills.
In the graph below, we compare the suction efficiency (cubic feet per minute, or
CFM) as the filter bag fills up. A standard filter bag's performance is represented
in red, the newly developed Cleantex self-cleaning filter bag is shown in green.
Over time, from left to right, the filter bag is going from empty to completely
full. From top to bottom, we see the level of suction being produced. Over time,
the self-cleaning filter bag retains near-full suction until the bag is full. Conversely,
a standard bag causes the vacuum to reduce in suction efficiency the more full the