I have a similar exhaust on my vacuum casting unit.
The hose runs from the vacuum unit to the exhaust hood next to it
which contains the kiln.
The hose runs from the back of the rubber pad, up the wall, and into
the top of the hood near the exhaust.
When I am casting the hood is already on to exhaust the kiln. When I
vacuum a flask I do have to remember to throw the switch to turn the
hood on, but I mix my investment under the hood so it is usually on
then as well. When the vacuum is fully engaged, you can watch the
slug of vapor move through the hose to the hood. The radiator clamp
on the exhaust port of the vacuum end is not tight, it just keeps it
from popping off, when I had it too tight the vacuum would get vapor
lock. Hope this helps.