Bathroom Smell II

I just got back from lunch and decided to take a short journey from the little shop to the mens' bathroom. I opened up the door, stepped inside and inhaled normally. I started to choke immediately as I could not fully breath with the foul smell that had infiltrated so sacred a room. Can someone answer this question for me? What bodily function can a person possibly perform that would create a stink the smells like a cross of shit and vomit? I doubt someone took a shit and then vomited in the same trip, so what could it possibly be? Anyone else have similar experiences with so foul a smell?