Pilot can shut of the system by pushing the button which will then illuminate the 'OVRD' text. Under normal condition, which is 'AUTO' the button is not illuminated. The ventilation system is not (as) critical from safety point of view, hence indication and operating can be integrated. A320 COCKPIT DIMENSIONS Here is a gallery of measurements I managed to gather in A320 cockpit visits. This will mitigate the possibility of mistakes, which is of great importance, since (as DeltaLima pointed out in the comments) the discharging of a fire bottle is not reversible, you only have one chance / bottle. The logic here is to separate visually and physically the indications and operating of a critical system. This video will explain how the CARGO SMOKE panel works. The button on the right will then verify the fire bottle discharge by illuminating the 'DISCH' text. GitHub - legoboyvdlp/A320-family: A high-quality Airbus A320 simulation for the open source simulator, FlightGear legoboyvdlp / A320-family Public Notifications Fork 36 Star 32 Pull requests 2 Actions Projects Insights dev 7 branches 0 tags 3,259 commits Failed to load latest commit information. Crew will then verify the alarm, and co-pilot will lift the red latch and activate the fire bottle by pressing the button under the latch. If smoke is detected by both sensors, the'SMOKE' text will illuminate. The logic in cargo smoke panel is such, that the black button is an indicator. I'm not specialized in Airbus, but here is a general answer for a part of your question: