During my trip to Houston (from Columbus, OH) last week as we were listening to the pre-take-off safety instructions, an alarm sounded, interrupting the take-off sequence. We were in an Embraer RJ-45 regional jet, and I was in my usual 2A seat. This seat is directly across the flight attendant’s control center (and kitchenette). As such, I was able to view the alarm panel and the ensuing activity. The alarm panel went off with an ISA 18.01 approved sequence that would make any control engineer proud. Of course, the flight attendant become flustered due to the significant amount of activity required to clear the alarm. First there was an audible alarm and associated flashing red light on the alarm panel. After a moderate amount of effort, the flight attendant was able to stop the audible alarm with the silence button, leaving the flashing red light. After some consternation, the flight attendant was then able to stop the flashing by pressing the acknowledge key. Whether or not silence and acknowledge functionality is required on a panel with only one alarm is debatable, but it was accurately implemented. Soon after the alarm was acknowledged, it cleared, and the system return to a “normal” state.
Apparently the alarm is associated with the smoke detector in the lavatory, and a quick check of the lavatory determined the there was indeed no fire or smoke present. It is also fairly well known to fire and gas system designers that smoke detectors can inadvertently activate for myriad reasons including mist and dust, so nuisance alarms are not unheard of. So, at this point you would figure that we would light the engines and hit the road, yes? No. In the airline industry the activation of an alarm (at least the smoke detector in the lavatory) is a very significant event that requires a significant follow up investigation. As a result, we returned to the gate, deplaned and called in the maintenance crew. The maintenance crew performed a full inspection of the lavatory, of the alarm system equipment, and performance a functional test of the alarm equipment. Only after that checkout were we allowed to re-board and continue our journey.
This struck me as a dramatic contrast with what I’ve seen in a lot of process industry plants. In many process facilities alarms occur so quickly and in such large numbers that many are acknowledged with little or no action taken to their presence. If the alarm clears quickly, virtually no review of the situation is performed. On the contrary, in many cases alarm equipment is allowed to stay in a failed state for long periods of time due to a perceived low priority. In some cases, with very unfortunate results. Alarms in the process industries do not get the respect that they deserve. This is mainly because there are too many of them, and both operating and maintenance staff are in relatively short supply. Perhaps the process industries can learn something from the airlines about alarm system design, operational response and maintenance philosophy.