Last night I turned on the steam generator in our master bath and let it run for twenty minutes with the shower door standing wide open. Then I opened the door to the bathroom and the mirror was clear in less than three minutes. The entire 120 square foot bathroom was completely clear of steam in less than three minutes without the bath fan ever being turned on.
So why would someone want to go to all this trouble?
Automatically starting of an appliance in mentioned throughout the electrical code. It doesn’t take an engineer to understand that the auto starting of an appliance while being worked on is dangerous. As long as the switch has an absolute off then there would be no problem but if it did have an absolute off then what is the need of the toggle switch.
Now if you have a situation where the moisture is a problem I would approach it with more than a bath fan.