I keep an aquarium as a hobby, and while cleaning a test tube I suspect I may have accidentally created poisonous hydrogen sulfide gas. Here is the situation: I had a glass test tube that was used about 6 years ago to do nitrate tests on saltwater using a Tetratest Saltwater Nitrate test kit. It was then neglected for about 6 years in storage presumably with some of the test solution intact which may have spilled out or evaporated leaving a layer of gray solid on the bottom, most likely zinc (which was part of the test), but perhaps more than just zinc. I had recalled a demonstration where a zinc penny was dissolved in sulfuric acid, so it occurred to me that I could clean this test tube with some 9.6% sulphuric acid that I had as a pH adjuster for the aquarium. I added the sulphuric acid and observed the zinc layer evolving gas, which I believed to be hydrogen, and at this time there was no odor observed. After several minutes I dumped the contents of the test tube into a sink with running water, at this time I smelled a strong rotten egg sulphur odor which I immediately ran away from and once I stopped I felt dizzy. I immediately left the room and looked up sulphur gas on the internet and found out about toxic hydrogen sulphide gas! I felt dizzy for several hours afterwards, and I thought I was going to die. I thought the reaction I was performing was zinc plus sulphuric acid yields hydrogen gas and aqueous zinc sulphate. According to my research zinc sulphate has no odor so I can't attribute the sulphur smell to it. I imagine there could have been more going on in that test tube than I realized. My question: is it possible that I actually made hydrogen sulphide gas, and if so in any significant quantity to harm myself? I feel foolish for being so careless, and I think I'm alright, but I'd like to understand what happened. I have a minor background in chemistry from my college days, but I am very far from being a chemist! I could use some help to understand this and thank you for your time.
It occurred to me afterwards that the solid in the test tube may have been precipitate created from the evaporation of aquarium salt water mix, plus whatever chemicals the nitrate test used in addition to zinc, as well as any compounds contributed by aquarium life (nitrogenous waste, etc.). Assuming that it was only zinc was foolish and may have been a catastrophic mistake. Also, what is the proper procedure to clean a test tube with unknown contents? Perhaps disposal would have been the proper move.