Well, I checked around my battery (Interstate MTP-93) and could
see anything where this hose would plug.
Somebody previously mentionned a vent kit. I have sent an email to interstate, will see what they say about that.
I don't know how this kit would look like, but I didn't see anything
on the battery where I could attach a kit, hose or anything else.
I'm also taking the car back to the shop that installed the battery.
They work only on MBs so they should know what they're doing, we'll see what they say.

W202 94 C220