Dust Extractor:- To achieve Class L an dust extractor must not allow more than 1 % of extracted dust to pass out of the filter to a "maximum allowable concentration" (MAK value) greater than 1 mg/m^3. To achieve Class M an extractor must not allow more than 0.1% of extracted dust to pass out of the filter to a "maximum allowable concentration" (MAK value) greater than 0.1 mg/m^3. There are several higher categories but Class H is generally the highest for normal trade use. To achieve Class H an Dust extractor must not allow more than 0.1% (can be as low as 0.005%) of extracted dust to pass out of the filter to a "maximum allowable concentration" (MAK value) less than than 0.1 mg/m^3. Class L is suitable for general work. Class M is specifically for mineral dust, man-made wood-based dust, oak and beech woods. Class H is used with anything that is a known carcinogen or has known health related effects. (Lead, cadmium, asbestos etc.) So the Festool CTL extractors are OK for more general work. If you are routing/sanding MDF or certain wood sorts (oak, beech etc.) then you must use the CTM series. Cleantek manufacturing different model to achieve the above class level. www.cleantekindia.com