Originally Posted by
kochleffel
I said not to use it on the plane, meaning don't plug it in while in the aircraft even if there is an electric receptacle at your seat. Aside from the fire risk in confined space, it draws too much current. Carrying it is not a problem.
The electric receptacle at the seat will allow a maximum of 75W to be drawn, so you could run an immersion heater from the seat without exceeding that. If you plugged in something that tries to draw more, the port will automatically shut down and stay shut down until whatever was plugged into it is removed. In theory, a 230V 300W immersion heater will pull 75W on 120V.
Additionally, any reputable immersion heater will blow their safety fuse around 85ºC, which is safe enough to prevent a fire. Many things would have to go wrong for something bad to happen. Not to say that this is a good idea, but it's less of a problem than it sounds. Even if you got it to work, it looks like you'd have to wait around 20 minutes for it to heat up water from room temperature to boiling.