That is a tough one. I would guess there are many (100? 1,000?) complicated organic carbon compounds in the smoke.

First, smoke is not gas, gas is not visible. Smoke is air borne moisture and various particles. Smoke is not vaporized oil. Oil becomes smokey way before it boils. You have lots of grease collected by the grease filter in your exhaust fan, that is most likely fine oil mist from the explosive water boiling.

But it is not important for you to know the composition of what is in the smoke. If it gives you pulmonary irritation, then you should minimize exposure to it. I don't think there are toxic substances in the smoke, irritating yes, poison no.

However, do be careful if the vessel you use is Teflon based non-stick. At very high temperature it can produce fume that can cause "polymer fume fever" - flu-like symptoms.

And if you are using tin coated copper ware, if there is zinc in the tin, that can cause "welder's syndromes"

dcarch

As long as it's not toxic, and just one time, I'll not worry too much. It's really very clean under the hood. Love the modern stuff, just yank it out, rinse it, and it's clean. So much easier than it used to be, so it stays clean (allergic and asthmatic, such is my cross!). Hm. I thought it was stainless steel, but I better check. Not teflon. I knew you'd get the whole chemical process worry I'm having. I'm much better today, but it was worrisome until it was all cleared. Other smoke hasn't done that to me ever. Weird! All I could think to do to get it to stop smoking was to pour it some place???, so I put it all into a larger pan, added a lot more oil and when it cooled down, tossed it. But getting that room clear was challenging! Three fans on high and open windows/door.

Thank you!