Looks like an exhaust system- the hose sits on the engine exhaust pipe and the blower on the ceiling vents the fumes out to the roof.
So you don't get carbon monoxide poisoning from running the vehicle in an enclosed bay. They hook that up to the exhaust of the vehicle and blow it outside.
What are the other two that are down hooked up to?
Nothing
Looks like extraction. Motor at the top, and duct through the roof…
To suck engine exhaust to the outside? Start the fan first, then hook the tube to the engine exhaust.
This would make sense, although I seem to remember being told that hosing can be used to pump warm air from the top of the warehouse down. So cheap , environmentally friendly heating.
If OP knows weather it sucks or blows, we might have this one solved!
You can see that the hose enters the center of a centrifugal blower, which is the inlet, so the hoses are sucking.
