Hah, what a surprise (not)! https://community.glowforge.com/t/ai...r-latest/28914

"We made a change to the design that we wanted to let you know about. We changed the Glowforge Air Filter shape from the original 'underneath' plan to one that more closely resembles the Compact Filter, and as a result, cannot support automatic on/off as we originally planned.

After many years of hard work on the original 'underneath' design for the Glowforge Air Filter, we’re still not able to achieve consistent performance that meets our high expectations for you. At the same time, we’ve continued to invest in improving the floor-standing design, and are beginning to mass produce it for you for delivery starting next month."