An extraction arm can be bent into position over the work, with a flow regulator for the suction. At the same airflow, a larger hood gives slower air in front of it, so a larger hood needs more air.
The air speed needed where the dust is released to pull it into the opening. The capture zone is the area in front of the opening where the air is fast enough. Recommended values run from 0.38 to 10.2 m/s, depending on how the dust is released.
Manufacturers state the airflow at full inlet, so we always show it with the inlet diameter. A smaller inlet or a smaller hose gives less air, with every manufacturer.
Dust in the air needs a large airflow at the capture point. Dust on surfaces needs a high vacuum. A vacuum cleaner built for surfaces does not remove dust that hangs in the air.