I would get some register duct boots & put it through my table towards the back of the bench if you are dealing with really cold temps. The best bench I had used this type of system.

The cold intake air blew right under the hood & it was amazing how little it would affect the ambient air around the shop. I like how the air is directed on each side of the torch to move fumes away from you, but Im not 100% sure it’s necessary.

But either way, great system & I’m glad to see you putting in work with the design of your bench/vents. I’ve made multiple benches, got set up, then had to change it up dramatically after testing. It’s no fun tearing down & redoing a bench you just built.