I have a Festool Dust Extractor. It seems as if the dust is somehow bypassing the filter bag and clogging the main filter. I cannot figure out why.

There are two stages of filtration in our dust extractors:

1. The filter bag
2. The filter itself

The filter bag is designed to capture larger particles of dust while some of the small particles may pass through to the filter itself through the breathable holes in the bag.

The breathable holes in the bag allow the extraction to stay consistent while the bag is filling to its maximum capacity.As the smaller paarticles of dust pass through these holes the filter is capturing the smaller dust particles.

Therefore if you use your dust extractor with very fine dust (such as concrete for example), it is possible that the filter has some dust already accumulated in it and if that's the case you may need to replace the filter.