What is the scuba like tank underneath the van , driver side, underneath van? on 1998 Dodge Ram Van 3500

Driver side, towards rear is an onboard generator. Underneath the generator, under the vehicle is what looks like a compressor tank. I want to remove this, but there is black hose that run from the tank that goes up and over the gas tank. I can't see where it terminates. Is this connected to the gas tank in any way? I don't want a vacuum leak if I acidently cut it off. Please advise. It doesn't seem as if the tank is connected to the generator. The tank looks like a scuba tank.

Asked by for the 1998 Dodge Ram Van 3500
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Sounds like you are talking about your evap system. your check engine light will come on. Do not remove.
No, it's not the charcoal canister,or anything related to smog equip, it's a rather long, about two feet in lenght , scuba tank-like in appearance. It has a drain plug at the bottom as well.
Is there red and green wire going to a small timer attached to it? Arabic writing on the side.