Each engine has an identical fire detection system, comprising two parallel detection loops monitored by a fire detection unit (FDU). Normally, both loops must indicate a fire to produce a warning. The loops are monitored and automatically disabled if they malfunction. Loss of a single loop produces a level 1 ECAM warning. Loss of both loops, or loss of an FDU, leads to a level 2 ECAM warning indicating loss of fire detection capability on that engine. If both loops break within 5 seconds, a fire warning is triggered. Each engine has a guarded fire button on the overhead fire panel. This lights up to provide fire indications. When pushed, the fire button pops out as a physical indication of activation. Pushing the fire button arms the squibs and closes the following on the affected engine:

The APU has an identical fire detection to the engine. When pushed, the APU button ... {TODO}

Each engine has two fire bottles and the apu has a single fire bottle. These are discharged by pressing one of the AGENT buttons situated near their respective fire buttons. The APU fire extinguisher may also be discharged automatically in the case of an APU fire on the ground. Secondary engine fire indications are provided by fire lights on the pedestal ENG panel, and a secondary external APU fire indication, together with a guarded APU SHUT OFF button, is provided on the EXTERNAL POWER panel. Once a fire is extinguished, the light in the fire button will extinguish.

Test buttons for each system are situated near their respective fire button.

There are two detector loops for the cargo compartments. Each loop has two detectors in the aft cargo compartment and one in the forward. A Smoke Detection Control Unit (SDCU) receives indications from these detectors and forwards them to the FWC which displays warnings on the CARGO SMOKE panel. If smoke is detected, the inlet and exhaust valves for the affected cargo bay are automatically closed. A single fire bottle is provided for both compartments. The aft compartment has two nozzles, and the forward compartment only one. When a DISCH button is pushed on the CARGO SMOKE panel, the bottle is completely emptied into the selected compartment. Smoke warnings will not extinguish once a fire is extinguished as the smoke will remain isolated in the cargo compartment and the smoke detectors are sensitive to the extinguishing agent.

A smoke detector is provided for the avionics in the air extraction duct. Its operation is detailed in Section 5, “Avionics ventilation”.

Each lavatory has a smoke detector. These are conected to another SDCU which transmits data to the flight warning computer (FWC) and cabin intercommunication data system (CIDS). Each lavatory waste bin has an automatic fire extinguishing system.