Interesting study conducted by NFPA. This is the 2nd study ive heard about testing LED versus xenon notification devices.
Concludes that xenon technology is viable for both direct and indirect viewing, while current LED technology does not provide the same indirect viewing performance as the xenon based product. So why can LED still be sold? At this point there’s are no indirect viewing requirements in NFPA 72.
Within the industry we are looking to address this in the next revision of NFPA 72 2016. To notify indirectly, you have to change the pulse width from 200ms to 20ms.
I was talking to a representative from Gentex at an ADI convention and he actually brought this up when I asked him if they’re planning on LED strobes at all. He told me that they are sticking with xenon and making it as efficient as possible for now, because of this issue.
I do think the concept of LEDs as fire alarm strobes is interesting but it is too early. I compared a Wheelock LED Exceder and a Wheelock NS, and the LED Exceder’s light output did not look very good at all compared to the NS, like I had to turn it all the way to 110 cd for it to be as effective as the NS on 30 candela.
This problem reminds me of the 15/75 strobes that they used to do, don’t see those much anymore… With those you had 75 candela directly in front of it and then the candela dropped the more off-center from the strobe you got, until eventually reaching 15 candela at 90 degrees from the center of the strobe.