Direct Visual Signaling as a Means for Occupant Notification in Large Spaces
The first two test sites were Home Depot stores located in Reading, MA and Danvers, MA. Invitations to participate were sent to members of the NFPA Technical Committee, NFPA staff, members and affiliates of the New England Chapter of the Society of Fire Protection Engineers and several deaf and hard-of-hearing organizations, including Self Help for the Hard of Hearing (SHHH).
A third test was planned for a Home Depot in Plaistow, NH and a fourth was planned for a Wal*Mart in Plymouth, MA. Both tests were cancelled after receiving only a few responses from persons invited to participate. A test was then scheduled to coincide with the NFPA 72 Report on Comments meeting taking place in Orlando, Fl.
Because the tests were taking place in businesses that were already occupied and open for business, the owners required testing to be done during early morning hours (6:30 – 7:30 AM) when there were few public customers in the stores. While this limited the ability to include “walk-in” participants, it did minimize the “Cry Wolf Syndrome” impact of the testing [i]. The early test time also affected the ability to get participants. In some cases it helped to get persons to come before or on their way to work. However, the time probably caused some people to decline participation.
Lighting in each of the locations was provided by fluorescent lamps. The Wal*Mart store also had skylights. The Illuminating Engineering Society of North America (IESNA) defines these spaces as “High Activity Spaces” with minimal sales assistance and products that are easily recognizable [ii]. The recommended lighting level varies with the specific use of the space. IESNA recommends the following levels:
Lighting levels for all three locations were within the range for general circulation and merchandise areas. The highest levels were found in the carpet and lighting displays of the two Home Depot stores. Ranges were on the order of 431 – 1937 lux (40 – 180 ft-candles).
The test at this location took place on August 24, 2005. There were 13 participants. The fire alarm system at this location was designed and installed to permit the audible signal to be disabled separate from the visible signals. This allowed the strobe lights to be activated without any audible signal.
Table 1 is a summary of relevant building and environmental information. Table 2 summarizes information about the strobe light system.
Table 1 - Building Information
Table 2 - System Information
The strobes at this location are located below the ceiling, at about the same level of the hanging fluorescent lights. The original design called for the strobes to be located over the aisles, between racks. Within each aisle, the strobes are spaced approximately 45 to 48 ft. Rack spacing varies with most 16 ft on center and some as much as 30 ft on center. Thus, strobe coverage might be 45 ft x 16 ft in order to provide a line of strobes in each rack aisle. However, after the system was installed, the rack layout was altered resulting in many lines of strobes not falling directly over an aisle.
The strobes at this location are the multi-candela type that is field adjustable. After the test it was found that at least one strobe was never changed from the nominal 15 cd eff. out-of-the-box setting.
Photo 1 shows a picture of a typical rack aisle with a strobe located directly overhead. A close-up of the strobe in Photo 2 shows the ceiling configuration and the location of the strobe relative to the building lights and structural steel.
Photo 1 - Strobe Over Aisle (Reading, MA)
Photo 2 - Close-up of Strobe (Reading, MA)
The test at this location took place on August 25, 2005. There were 12 participants, eight of whom also participated in the Reading test. The fire alarm system at this location did not permit the audible signal to be disabled separate from the visible signals.
Table 3 is a summary of relevant building and environmental information. Table 4 summarizes information about the strobe light system.
Table 3 - Building Information
Table 4 - System Information
The strobes at this location are located on a suspended acoustical tile ceiling at the same level of the building’s fluorescent lights. The design and installation resulted in most strobes being located over the aisles, between racks. Within each aisle, the strobes are spaced approximately 48 ft. Rack spacing varies with most 16 ft on center and some as much as 30 ft on center. Thus, strobe coverage might be as low as 48 ft x 16 ft in order to provide a line of strobes in each rack aisle.
Photo 3 shows lines of strobes on the ceiling. Photo 4 shows an aisle with strobes directly overhead. Photo 5 is a close-up of a strobe on the suspended ceiling.
Photo 5 - Close-up of Strobe (Danvers, MA)
The test at this location took place on October 28, 2005. There were 22 participants. Two participants had also taken part in both the Reading and Danvers tests. This test coincided with the Report on Proposals meetings of the NFPA 72 Technical Committees. The participants were all Technical Committee members and included almost all members of the Notification Appliances Committee.
The fire alarm system at this location was designed and installed to permit the audible signal to be disabled separate from the visible signals. However, the manner in which this is effected results in a single audible chirp when the system was activated. After that first chirp, the audible signals stop and the strobes continued to operate.
Table 5 is a summary of relevant building and environmental information. Table 6 summarizes information about the strobe light system.
Table 5 - Building Information
Table 6 - System Information
The strobes at this location are located on the bottom of the bar joists supporting the ceiling/roof. The florescent light fixtures are approximately 8 - 12 in. below the bar joists. The design and installation resulted in strobes being located over most of the main aisle and circulation areas. However, not every merchandise aisle has a row of strobes overhead. Typically, the strobes are over the main aisles and over every third to fifth stock aisle.
Photo 6 shows the ceiling configuration with strobe lights located on the bottoms of the bar joists.
Photo 6 - Strobes Located on Bottoms of Bar Joists (Kissimmee, FL)
[i] R. Schifiliti, “Fire Alarm Testing Strategies Can Improve Occupant Response and Reduce the "Cry Wolf" Syndrome”, NEMA Supplement in Fire Protection Engineering, Society of Fire Protection Engineers, Bethesda, MD 20814, Fall 2003.