Exhaust hose "flapper" for garage door

["Kent Sullivan" <kentsu@corvairkid.com>]

Hi,
 
I'm working on the design for a shop for myself. I'd like to investigate
having a "flapper" in each roll-up door like those I have seen in
service station roll-up doors for years. The idea is that a hose coming
from the tail pipe exits the building through the flapper--handy when
the weather is not summer-like.
 
Does anyone have a source for these?
 
Thanks!

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