A common problem in plumbing remodeling is figuring out how to run new vent lines when access to the existing drain-waste-vent system is blocked by some structural element.
One option is an air admittance valve. These valves are gravity-operated devices that respond to the negative pressure of draining water and open to let air in. Then gravity closes the valve, keeping sewer gases out of the room. Depending on the valve and the size of the vent, AAVs can support one or multiple vent lines. Local codes govern the use of AAVs in place of vents.
About an hour to cut and assemble five or six pipes and fittings
PVC saw or backsaw, miter box or power miter saw, deburring tool, felt-tip marker
Cutting and measuring pipe, working methodically
Sketch drain/vent assembly; clear a path for the pipes
Primer and cement for your type and size of pipe, P-trap, air admittance valve, drain pipe