How to open this air return duct between joists

Question

I got dead rodent in return duct, at least I hope I will find it there. My returns on bottom and supply on top. Strong smell from return in one bedroom. Attached is pictures how this duct look from a basement. One end is next to window (where it goes up to the room). Another picture is where sheet of metal meets another one. It's about 8ft long.

I need to take that section out, I believe this is where rodent will be.

How do I take this piece out? Never took ducts apart, need some guidance, don't want to break anything..

Answer 1

The thing that runs perpendicular to the duct sheeting looks like a standard z folded clip. Not sure of the mechanism of the sides, but they are probably simple slots.

After laying plastic sheeting on the floor and donning a dust mask and gloves, I'd try simply shoving the bottom of the duct upwards. It should buckle and come apart, dumping everything onto the floor below.

Re-assembly is probably easier if you use sheet metal screws and foil tape.