In grad school around 1980 I was doing some reaction under a hood using DMSO as the solvent and for some reason it was converted into DMS (DiMethyl Sulfide) and

In grad school around 1980 I was doing some reaction under a hood using DMSO as the solvent and for some reason it was converted into DMS (DiMethyl Sulfide) and we discovered how bad the vent system was in the building (it was terrible). The building was evacuated and they forced me to go back in to look up how toxic DMS was (stupid grad students are expendable). Thankfully while it is chemical related to Hydrogen Sulfide it was not all that dangerous and in a couple of hours it cleared. However if you ever get to smell it you will run as far as you can and the odor is unstoppable. Forget tear gas, toss some of this into a building and watch everything run out. Cleaning out the hood was a terrible experience.