Vent hose behind Webasto on 2018 c302

[Jclima]

Does anybody know what this hose is for? I was working on my Webasto heater and I noticed this hose was pulled apart. It is directly behind the heater under the oven. Looks like the vent for something. At first I thought it was the vent for the holding tank but according to the manual that is on the starboard side. I was able to seal it back together but curious if anyone know what that is for.

 

[Mike and Sarah]

That duct looks like same material the Webasto uses. Cold air return? Duct to supply heated air to the cockpit like the r29 has.