I have been searching online for a couple weeks now without any luck.

There are plenty of secondary lint traps that install along a run of standard 4” rigid metal duct. I’m looking for a secondary lint trap that I can install in my rectangular rigid metal dryer duct that runs from my laundry room up to my attic and out through the roof. This duct runs behind my laundry room wall, and I’m hoping to cut into this duct to install the lint trap so that it’s right in front of your face if you’re standing at the dryer. Trying to avoid the “out of sight, out of mind” problem.

As you know, venting up and out through the roof is a bad idea, mainly because the vent is out of sight (there’s a much greater chance of dangerous lint buildup, leading to fire, etc.). So...if there were another way for me to vent the dryer, I would have done it.

Right now, the dryer is venting into the garage. That’s where my home’s previous owner vented it after the upward vent got clogged. Even with the garage door open, there’s a LOT of moisture collecting in the garage. It’s not ideal, but I’d rather not exhaust upward without that lint trap in place.

I’m looking for rectangular because I don’t see much room to replace the rectangular duct with standard round 4” rigid metal duct. The wall has 2x4 studs, so 4” duct won’t fit. And building that wall out another 2” from top to bottom also seems infeasible because the wall has what appears to be a metal sheet immediately behind the drywall. I can even see this metal sheet running all the way up to the top of the drywall (I can see it from the attic).

Thanks for any leads you have on a rectangular lint trap. I appreciate it!