Odor around air compressor

That same odorant was used in other explosive gases that have no natural smell. I have a bottle of that old R12 replacement that smells like propane. That stuff was short lived because it was blowing up in accidents.
That being said, sulfur smell can happen naturally too. My basement sump pump smells like *** all the time. Stagnant water is funky. With these things in mind take a walk around the area and try to pinpoint the source.