Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

They don't produce much fumes when running the way you want it to run. I had an M90 running on my desk for 4 hrs 56 min on a single full tank. I could not notice any severe deterioration in air quality. Come to think of it, I don't recall any air quality problems. That said, my hvac system circulates the air pretty well.

I see no issue with a short run indoors.

Gil