I've only done the electrical portion, usually refits of existing kitchens with existing fan hoods. Sometimes, there's only an exhaust fan; sometimes there's one switch, sometimes two; sometimes one of the fans is a 2-speed, etc.
In any case, the basic requirements, when tripped, are (1) that the intake fan goes off and the exhaust fan goes on, regardless of the switch position, and (2) that anything electrical under the hood lose power.
As for what I've observed, they run a wire with melt links above the grease traps that is under tension, and when broken trips the gas (if there is any) to shut off and the extinguisher to discharge.
Plus, ther is one or more manual pull stations, typically near each kitchen exit door, that trips the system when pulled. All of these are operated by a thyin wire rope inside EMT with pulleys in the elbows.
Every system is different, but the basics are the same. If the microswitches can handle the current, they can control the fans directly; otherwise you need to control, or add, contactors if necessary.
The simple thing to keep in mind is that you need to place an NC switch in series with the intake fan's switch, and an NO switch in parallel with the exhaust fan. Unless you can use a single section as above, as I do.
