"easaman" brightens my memory, we had few fire extinguisher related mishaps during years.
One a/c type have very similar studs for squib and bottle used indicator, SB calls to install extension to one of those studs, which is also slightly different diameter to avoid wrong connections. One aircraft found without these extensions, and off course at least one bottle was connected wrong way.
This remains us to perform requested system tests without any shortcuts, this a/c type requires time consuming and relatively complex test for whole eng fire ext system time to time, with multimeter. Its purpose serves to find hidden problems or system faults. Four engine, two bottle/engine.
Another a/c type found with completely empty fire extinguisher bottle, noted after removal for weight check. It wasnīt fired, just empty with unused cartridge.
Saw numerous accidentally fired cargo fire extinguisher on one a/c type, problem is bad design for shot switches on cockpit roof panel. System to be tested daily by pilots, shot and test buttons are both on roof panel... and shot buttons have only flimsy plastic cover. It is very tempting button when your list says "press to test". PSUHHHH!!!
Not nice if you have loaders in, or if this happens during maintenance when there is people working in cargo bay.
One test for pilots oxygen masks found hidden problem with mask. This remains me for importance of routine tests, even smallest one.
Test calls to visually inspect, and test mask by actually don it to make sure oxygen is flowing and regulator is working.
This mask was broken, first it didnīt pressurize rubber bands to allow don mask easily (remember this should be done easily in possible emergency). After small fiddling with triggers, mask was pressurized but now it didnīt left oxygen out from bubbers bands... so mask wouldnīt stay on head. Mask was clearly u/s,but tried one more time just to make sure positive fault.
Suddenly mask deflates, and at the same time oxygen regulator locks somehow and prevent flow in or out.
In that case, you have mask which sits tightly on your face and you cannot breath...
I would say this is not nice if you have cockpit filled with smoke, or pressurization is gone.
Been quite serious with tests or inspections for emergency equipment, those should work w/o any problems when needed. There is no time to start troubleshooting or start finding missing smoke goggles etc etc...
Those things, in good case, never see real action but they must be there. In perfect working condition.