Venting Indoors

Get up on the RV roof and extend the ABS pipe thought the building roof. Don't even need to glue the pipe, just piece it together.

I would use a 1.5" PVC pipe from the RV black tank vent to outside the building. Yes you will need to drill a hole in the building wall or roof.

Use the black tank flush often, add one if needed. keep the tank valves closed except for the brief time when dumping. Use plenty of odor preventing chemicals. Other than that, extend the vent outside as stated above.

Are you sure that it is the RV vent and not another building drain pipe which is open and allowing fumes to come back into the building?

x2 on all other drains being capped and traps filled with water.
extend rv vent to outside. I would just use some cheap light weight dryer vent hose.

If you are keeping the RV connected via drain hose, be sure to CLOSE both grey and black tank valves!

Otherwise when it gets windy outside the septic/sewer stack vent pipe can create enough reverse air flow (downdraft) to push the septic/sewer gas back into the onboard tanks and out the tank roof vents into your interior space.

I would also second the idea of connecting your roof vents on your RV to a roof vent for your building to the outside.

However, I would not recommend using all rigid pipe, you WILL want some FLEXIBLE pipe to connect to your RV roof vents. This allows for any movements of the RV suspension or any slight movement of the wheels without putting unneeded stress on the RV plumbing.

You also do not want the extra pipe weight to rest on the RV plumbing, that extra weight could possibly break or damage the on board tanks or push the vent pipes down into the tank which would be bad..

if you're valves are open your going to have a poo pyramid to deal with too

The automotive world has an answer.. a Flexible exhaust hose. remove the "hat" from the stink pipes and use exhaust extention to take 'em up through the roof.

Seal to the roof as you would a toilet vent line but cap it with a "hat" like the one on the RV so rain does not enter it. I would also screen the top for insect control.

When done leave them as roof vents.

I believe a Studor vent would resolve the issue without having to run a pipe through the roof. Just install the Studor vent on the RV roof vent.

Studor Vent-
Air Admittance Valve

Move the trailer outside? Park next to the sewer clean out to dump.