Sulphur odor in upstairs area
There should not be any plumbing vent, dryer vent, bathroom vent, etc. stopped inside your home, in the attic or otherwise. Everything should be vented outside, usually through the roof. Sometimes vents get stopped short or partially blocked and can cause this kind of problem.
If a vent pipe on the roof has a partial blockage (leaves, ice, sticks, birdnest, etc.) this can cause sewer gas inside the home. What happens with a partially blocked vent is that whenever water drains through the drain/waste/vent system, it will create another "vent" by siphoning the nearest trap water out. That allows sewer gas back into the home. (That's what traps prevent when functioning properly.)
Let us know what you find.
If you can't find a vent ending inside the attic, your hubby needs to go up on the roof (carefully) with a flashlight and check the vent pipes for obstructions. He can hand-clean out what he can reach, and then flush the vent stack down with a garden hose sprayer. If after hand-cleaning, there is still debris down the stack that a garden hose won't dislodge, then it has to be snaked down with a heavy-duty (rented) plumber's snake from top to bottom, and then flushed.