[curious]

why is the suction not near the laser lens ?
where the smelly fumes are.

anyone has experience to change it ?
now i have a huge ventilator on the bottom, a lot of noise and still i can smell the burning material.

[cinematic2]

Because during engraving movements might be too quick to suck.
Second reason is the weight of machines head.

[bpoulin]

CNC routers utilize this kind of stuff, but they move a lot slower than a laser engraver. Your best bet is to find a place to install a small computer fan blowing from front to back of your table top, it will blow the smoke towards the back edge where the suction of the air extractor is the most powerful. My machine has 2 of these blowing at this kind of direction ^ from front to back, not crossing, but both pointed at the center rear part of the engraving table.