This has happened a few times since I moved into my current house about a year ago; every once in a while, I'll get a faint, brief whiff of rotten egg smell that I am unable to locate. Then, after a few minutes it will be gone and not be smelled again for months.
Today it happened again so I went around sniffing everything to try my best to find the source, trying all the typical emitters. I turned on the hot water and sniffed all the faucets; nothing. I sniffed the sink bowls and the toilets; nothing. I sniffed all the gas appliances as well as the walls where the gas lines drop down from the attic; nothing. And then it was gone again.
Am I going crazy from hydrogen sulfide poisoning? What are some other potential sources I might have missed? Is this the precursor to some gas or plumbing problem that's about to become really really expensive?