As building alarm systems get more pervasive and sophisticated, all best efforts can still not prevent unanticipated operation. Here’s one incident that I don’t mind not being a part of…

…On August 7, 1997, a training department representative at the Haddam Neck nuclear generating plant was taking pictures of the fire system indicators and controls to develop training aids to upgrade the Halon system training manual. The training representative was using a Canon PS1001, Power Shot 600 digital camera to take pictures of the ANSUL Autopulse 2000 Halon control panel mounted on the wall in the control room. When the training representative took a flash photograph of the alarm reset/silence push buttons inside the Fire Detection System (FDS) control panel, the first flash caused an annunciator inside the panel to sound. The cabinet door on the panel was closed, and an examination of the front panel showed no lock-in alarm indications. The cabinet door on the panel was reopened, and a second flash photograph was taken within two minutes of the first picture. The second flash caused a second alarm with a different tone, indicating that system actuation was imminent. Within three to five seconds of the second flash, Halon discharged from the overhead nozzles.

Subsequent testing confirmed that the light from the camera flash affected an EPROM microprocessor located inside the Halon FDS control panel. The camera flash caused the normal one-minute delay to be bypassed and resulted in an almost immediate actuation of the Halon system. Discussions with the manufacturer indicated that a strong light source could cause an unpredictable perturbation within the EPROM, depending on the light intensity and the angle of incidence to the circuitry through the EPROM's window…

[Excerpted from: http://www.hanford.gov/lessons/sitell/ll98/199805.htm After indoor Halon discharge, it is routine to conduct hearing tests on the occupants. It is supposed to be a very noisy event.]

Wow!

Whenever I install an EPROM as a permanent fixture I always fit an opaque sticker over the window to keep out stray UV sunlight etc.

Surely the manufacturer of this panel wouldn't have omitted something that simple?

Yes, I'd agree with you Paul. Maybe something like a firmware change got sent out unintentionally unmasked?

Have seen a few EPROMs on boards for equipment like Fire Alarm / F.L.S., Security equipment, Lighting / BAS / EMS controllers, which were missing the label that covers the erase window.

To avoid the same situation of accidental erasure, I place a thin strip of duct tape over the window, and build up a few layers. Hoping this may at least reduce the problem.

Maybe the glue didn't hold well on these EPROMs, or maybe it as Bjarney said - Firmware upgrade - but the PROM never gets recovered after the flash.

It's easy to see the ones with firmware upgrades which were recovered. The label has revision notes on it, or a small label covers the original sticker.

Nevertheless, that story of Bjarney's is a real eye opener!!! Sure makes me think twice when taking pictures of equipment!

Q?: How do you ruin someones whole day/week?
A: Uncover an EPROM and ask them to snap a picture of the board!

Should be submitted to the "Poop Occurs" section of trade magazines.

Scott