Gilbert Industries, Inc.

5611 Krueger Dr.
Jonesboro, AR. 72401

May 31, 2001

Mike Shulman, Senior Staff Engineer
Underwriters Laboratories, Inc.
1655 Scott Blvd.
Santa Clara, CA. 95050-4169

Subj: My letter dated May 1, 2001 in response to Paul Lloret’s letter 4/16/2001

Jim Beyreis letter dated May 1, 2001

Your letter dated May 8, 2001

UL Status of the 11/22/00 Proposal dated May 11, 2001

Dear Mike,

Regarding SG4.2.3.1 of your May 11th status report: How does doubling the charge time of a P/L exit that is uncharged at the start of activity every business day relate to an emergency electrical sign that is maintained at full charge 24/7 and may be fully discharged only once or twice a year? And why doesn’t a P/L sign have to comply with requirements similar to an electrical signs battery discharge and undervoltage test?

On March 16, 2001 I wrote to Tom Castino regarding the reduction in measured luminance performance proposed for introduction into the UL 924 standard. The 0.06 ft/L minimum that had been part of the standard, as proposed, is to be removed. Subsequently, I learned from your Mr. Shallhammer, that the 0.06 ft/L minimum was not based on scientific determination:

"The basis for the 0.06 ft-l minimum, as we understand it, is that it represents what the tritium technology was capable of producing, and that it does in fact represent a level that is visible (as verified by observation tests) from the prescribed distances." (Mr. Shallhammers 4/2/01 letter).

Using this logic to establish 0.06 ft/L as criteria, along with 5 minutes of "dark adaptation" before subjectively determining readability without a reference is contrary to existing science and logic. I believe that UL924 should establish a realistic (real world) minimum for exit signs…and the 5 minutes in total darkness criteria should be given a reality check. NIST and the LRC have published independent studies that clearly show that 0.06 ft/L is the wrong number. The right number was originally published by Schooley/Reagan and is supported by both the NIST and LRC conclusions. The present proposals for UL924 could permit emergency exit signs to be Listed with luminance performance levels of 0.023 cd/M2. That represents a fraction of the tritium luminance level that has been summarily rejected as unsuitable by both NIST and LRC studies. UL is well aware that the performance of emergency exits is going down… way down!

NFPA has been advised by Underwriters Laboratories at least twice in public meetings that the adoption of the 2000 Life Safety Code would result in UL Listed exit signs that are considerably dimmer than what the Means of Egress Committee had become accustomed to seeing. This, I believe, will jeopardize the safety of those trying to egress a building in order to escape from a fire or events such as Oklahoma City, the World Trade Center, hurricanes, tornado’s, etc., etc. NFPA has a lack of interest in establishing a meaningful minimum since adopting their new "performance based standard". That has been left up to UL, who now shares that liability with the formation of the "STP". Liability is a key word, defined herein as being held responsible.

Regarding direct view exits… We appreciate the recognition from UL that "LED exits…were developed by Gilbert Industries". We are proud of the fact that we gave birth to the LED EXIT. As you know, and as a matter of history, all Gilbert LED exits were originally tested and Listed by UL using the Kodak gray scale comparison method. Unlike UL’s observational method, that test was referenced to a standard exit illuminated to 5 ft/c. To further illustrate performance, I will (at your request) provide spectral radiometer charts of the results of a comparison of the total flux provided by a direct view exit and a Listed cavity illuminated exit. The cavity sign used in this comparison (a Listed Gilbert product) provided an average luminance of over 5 ft/L (>17cd/M2). In this test, the cavity sign produced a total flux of 6.49 uw/cm2. The direct view sign produced 6.84 uw/cm2. Mathematically reducing the measured luminance of the cavity sign to UL924’s minimum of 2.5 ft/L would result in the direct view exit providing twice the flux of the Listed cavity sign. The direct view exit is a viable and useful product because it is a high performance product providing better visibility, more luminance and longer emergency run times than its competition.

In recent months, UL has commented that this dialog is intended to exclude non-electric technologies from UL Listing as emergency exit signs. Categorically, that is false. The issue is that all technologies should be included and Listed only when that technology meets an identical (or even similar) performance standard. In the case of Tritium, according to UL, the published analytical minimum was excepted because "…it represents what the tritium technology was capable of producing….". That, plus 5 minutes of dark adaptation immediately prior to the observational visibility test did not maintain the established standard as defined by science and accepted by UL and the NFPA.

It is the ability to immediately locate, identify and follow an exit sign to a safe egress that has been brought into question. Providing an alternative means for testing is a perfectly acceptable practice when all testing uses the same reference standard as the existing method. That was the logic behind the Kodak gray scale comparison test. It is the result of the test that determines overall performance, not the incapability of the technology that determines the standard. This later practice established different performance levels for different technologies… which is precisely where UL924 resides today, and one of the reasons that UL924 is no longer an ANSI Standard. The current 924 proposals further corrupt the standard, and according to UL will result in dimmer exit signage. An exit is an exit is an exit. That is the issue, and compromising public safety should be understood as unacceptable. The future should be about further raising the performance and safety level provided by products Listed to UL924 requirements, not reducing that level to accommodate substandard performance.

Thank you for your response to my letter. We look forward to the first "STP" meeting.


Thomas W. Burnet

Manager of Product Development

CC: L. Knoblauch, T. Castino, W. Schallhammer, J. Beyreis, D. Snyder.


To UL / April 17 From UL / May 8
From NIST / April 20 To Dept. of Labor / May25
From UL / May1 To FEMA / May 29
From FEMA / May 2 To NFPA / May 30
From Dept. of Labor / May 4 To UL / May 31

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