While cutting wood on the mill, I observed a lot of small particulate matter in the air. To mitigate this, I designed a simple adapter to join a cheap aftermarket shop-vac filter to an HVAC fan system from an old K-40 laser cutter.

The adapter fits inside the filter and into the duct. The duct is clamped onto the adapter using a pipe clamp, and to the filter using a length of rope with a knot at each end.

A knot at each end prevents the rope from slipping through the hole in the adapter and the corresponding hole in the filter. Changing the filter is as easy as undoing the knot.

Here it is installed in the temporary frame. A suitable replacement for the HVAC fan I already had is this bathroom exhaust fan.