Potential
Some fairly direct comments here it's nice to see that you remain pragmatic and calm.
Shouting " fire" IMHO would probably cause more probs than it would solve .
The real issue is that , as has been pionted out, action by passengers could easily create more danger . What if the fumes had been from a main gear wheel bearing on the left hand side ? the fumes could well go into the pack inlets causing smoke /fumes in the cabin . Opening a door on the left hand side could allow flames fumes directly into the cabin .
Bottom line ,if the cabin crew are not initiating an evac with their trained procs. neither should the passengers .
It is v important the captain keeps all parties in the loop but NOT when he/she is in the middle of dealing with the situation .