For my old 5.5 Watt diode laser I have made a box with a small PC fan. Hose diameter is 50mm and it actually worked quite well. So it does not take much to get rid of the smoke.
I used a 5" extractor fan piped outside via a home made box filter using carbon cooker hood filters as they are readily available. I drilled 3 x 4" dia holes through the case into the side of the laser case for incoming (workshop air) and the extractor is in the back. Works very well for my 1000 x 600mm bed.