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5611 Krueger Dr.
Jonesboro, AR. 72401
870-932-6070

April 17, 2001

Underwriters Laboratories, Inc.
Northbrook, IL

Attn: Mr. Tom Castino – Corp. Vice Chairman

Dear Mr. Castino,

On March 16, 2001 I wrote you (and others) regarding certain provisions in the current UL proposal for photoluminescent exit signs. I did receive a response from your William Schallhammer in which he stated (in part): "….UL requirements for internally illuminated EXIT signs have taken into account the results of outside agencies’ research reports (such as NIST), UL’s own research, and input from various other concerned parties."

I have been in contact with Dr. Belinda Collins of NIST and Dr. Peter Boyce of the Lighting Research Center. These two individuals are among the most learned reference points and authors of significant studies regarding the performance of exit signs in the USA. Their conclusions call for higher luminance levels. Specifically, the studies by Dr. Collins conclude that a minimum level of 10 cd/m2 is required for reasonable visibility in both clear and smoky conditions. Dr. Boyce concludes that the luminance of an exit sign should be 15 cd/m2 (avg.) and 8.6 cd/m2 (min). The Schooley/Reagan report that I referenced in my 3/16/01 letter called for 5.0 ft-Candles (8.6 cd/m2), the minimum luminance required of electrically operated signs by the NFPA and UL for over 20 years. Further, that requirement is still accepted by the EPA Green Lights program as their minimum standard. It is interesting to note that both Collins and Boyce agree that the best overall performance is a brighter sign, 20:1 luminance uniformity and a high contrast ratio. Collectively, this is very similar to the points raised in Schooley/Reagan. I do not find any reference, scientific study or opinion (other than UL) that indicates, concludes or even suggests that a minimum luminance level of 0.205 cd/m2 (Tritium) would be suitable for exit signs, much less the .02 cd/m2 provided by photoluminescent. All science and reason suggests that the minimum luminance requirement should be equal to or greater than 8.6 cd/m2.

Mr. Schallhammer stated that: "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."

"Visible" in this context is visible after 5 minutes of dark adaptation time and acceptable because .06 ft-Lambert’s (0.205 cd/m2) is all that a Tritium sign is capable of producing. I do not believe that either is a suitable parameter for acceptable performance of Life Safety Equipment. Today, the current UL proposal reduces the minimum measurable requirement to zero and provides the means for subjective testing performance levels of less than 10% of Tritium luminance, or less than 1% of the long standing 5 ft-Candle requirement.

Since UL924 lost its ANSI classification some time ago, the ramifications caused by adopting the 11/22/00 proposal are somewhat minimized. However, I believe that UL maintains a leadership position among NRTL’s. As a leader, UL should take responsibility, research the contemporary science and studies, and develop forward thinking requirements particularly for issues directly involving the public and life safety.

Mr. Schallhammer made a statement in an earlier letter that " Your letter has clearly been prompted by the introduction of photoluminescent products into the scope of UL 924 and NFPA 101. The unique characteristic presented by photoluminescent products relate to their dependence on an external charging source and their dynamic light output degradation."

The emergency lighting industry has a great deal of experience in dealing with and meeting the requirements of UL924. It should have come as no surprise to UL or NFPA that this industry stood up to be counted when the longstanding requirements for luminance levels became unimportant to the NFPA and UL. This industry had just spent millions of dollars in Listing fees and product retooling in order to meet the 1998 requirements. Further, the functionality of an exit sign changed from one that must be readily visible to one that only had to be barely visible after 5 minutes of dark adaptation time. My letter, and the industries disagreement with the position taken by both the NFPA and UL is caused (in part) by the NFPA 101-2000 change to a "performance based standard", but more so by UL’s irresponsible reduction of requirements. The whole of the lighting industry disputes the veracity of this change, and this change is substantive because as written, exit signs (including electrical signs) are no longer required to meet any minimum standard measurable level of luminance. It just barely has to be visible after 5 minutes of dark adaptation time.

Photoluminescent is not the problem, nor was it the cause of this problem. That is a separate issue, and one in which Mr. Schallhammer has correctly identified. In the 11/22/00 proposal, the external charging source is an integral part of the photo-luminescent product. It is a system containing 2 parts: 1st, the sign. 2nd, the charging source. In order to properly use the photoluminescent sign, that minimum charging source must be specified and included in the installation. At the last 924-IAC meeting, Mr. Schallhammer stated that P/L had to be understood as a hybrid of externally and internally illuminated technology and therefore illuminated to 5 ft-Candles during normal operation. These issues are not addressed in the proposal, and have nothing to do with the aforementioned problems created by the dissolution of requirements in UL924.

I am aware that the UL Fire Council is meeting on the same dates as the NEMA Lighting Sections semi-annual conference. I have been told that this issue is an agenda item for the Fire Council meeting. I can assure you that this is an agenda item at NEMA. It is my hope that the fire council understands what is at stake and at risk regarding the 11/22/00 proposal and resolves to insert the 8.6 cd/m2 minimum luminance requirement for ALL exit signs. In order to save time, I have taken the liberty of sending copies of this document to all UL personnel that I know to be involved.

Sincerely,

Thomas W. Burnet
Manager of Product Development

Copies: Loring Knoblauch-Pres/CEO; William Schallhammer-Asst Ch/Eng; Don Snyder; Wayne Menuz; Mike Shulman

Att: CSA Test Report on Exit Sign Luminance.

REFERENCES:

* Collins, B. L., Dahir, M. S., and Madrzykowski, D. 1992. Visibility of Exit Signs in Clear and Smoky Conditions. JOURNAL of the Illuminating Engineering Society. Volume 21, Number 1, Winter 1992. Pages 69-84.

** Boyce, Peter. Draft Specifications and Testing Protocol for Visually Effective and Energy-Efficient Exit Signs. Troy, NY. Lighting Research Center.

*** EPA Energy Star Labeled Exit Sign Specifications. www.epa.gov/nrgystar/purchasing/6j_exitsigns.html

**** Schooley, L. C., and Reagan, J. A. 1978. Perceptual Tests of Exit Signs.

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2001


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