For anyone interested here’s some details on a $12 DIY air assist to automatically power on the air pump and exhaust fan once a file is begun and shut them off when complete. On my RD3445G controller, the 6 pin CN1 is the air assist module. During operation pin 6 (+24V) and pin 4 (Status) output 24vdc. I had expected to use pin 5 (Wind) but found it outputs 24vdc only when the laser is firing ie between every raster line engraving it would briefly shut off then back on. Pretty sure the equipment would hate that. Luckily pin 4 outputs continuously until the file is complete.
Once I figured this out all I needed was a $12 relay from Amazon. I got a 10a relay with 24v coil, and spliced it into the red (neg) 120v wire of one of the integral 120v outlets on my laser. Wired the coil to pin 4 and 6 of CN1 and tested- total success. The wiring of the built-in 120v jacks are a pitiful 18awg, but my pump and fan together pull 3a so its sufficient. I also wired a rocker switch ($2) directly to that outlet so that I could have manual control of the equipment if I needed it.
The only difference between this and the much more expensive and labor intensive “Ultimate Air Assist” is that it apparently automatically decreases the air flow during engrave and maxes it during cuts. Anyways- thought I would share as it took a bit of head scratching but ultimately worked out perfectly.