I came across this today. Sorry for the bad picture. Obviously its purpose is to shut off the air handler in an emergency. It’s in a Townhome that’s a business on the first level and residential on levels two and three. All three levels are serviced by one HVAC system. Is it so that the fire department doesn’t have to look for the thermostat? What are the primary concerns? Is it an issue with gases on the first floor being spread to the upper levels? Or could they be worried about gases inside somehow being exhausted outside?