ARCHIVED – Fire research v13n1-8

Volume 13, Number 1, March 2008

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Photoluminescent stairwell installations facilitate evacuation from office buildings

In 1993 when a bomb exploded in the underground garage of the World Trade Center (WTC) in New York, thousands of occupants had to evacuate in complete darkness, as the generators providing power to the emergency lighting were destroyed. In response to that event, photoluminescent paint was applied in the WTC stairwells to guide occupants out of the building in an emergency.

Photoluminescent material installations used in study
Photoluminescent material installations used in study

The installation of this photoluminescent material was put to the test on September 11, 2001, and proved to be useful and reassuring to at least one third of the survivors interviewed. Following the events of September 11th and the blackout of August 2003, New York City passed a by-law, in 2005, making photoluminescent marking mandatory in all new and existing high-rise commercial buildings.

Today the use of photoluminescent material (PLM) systems in buildings is gaining acceptance in North America as a valuable safety feature. The material is installed as a continuous marking along the means of egress and glows in the dark when the power fails or when the lighting is obscured by smoke, helping occupants find their way to safety.

The American Society for Testing and Materials (ASTM), New York City, and the International Organization for Standardization (ISO) have all published installation standards for PLM systems, but the installations proposed have never actually been tested by occupants evacuating a building. The standards differ from each other in terms of the location and quantity of material deemed to ensure a safe evacuation.

To remedy this absence of data and identify what constitutes a suitable installation, NRC-IRC fire researchers, in collaboration with Public Works and Government Services Canada, conducted an experiment in a 13-storey high-rise office building with four identical windowless stairwells, housing over 4,000 occupants. They tested the effectiveness of three different PLM installations and compared them to a stairwell under emergency lighting conditions and no markings (see table below).

An evacuation drill was carried out with no advance warning to occupants regarding the day and time of the exercise. The number of occupants who used each of the four stairwells during the evacuation drill was similar, and all stairwells quickly became densely populated, which meant that the evacuation movement was slow. Data were obtained by using video cameras positioned inside the stairwells and through a questionnaire distributed to occupants following the evacuation.

Stairwell Type of Marking (see photos) Description of requirement
C None (mean lighting level of 37 lux) Meets NBC requirement for emergency lighting
A L-shaped marking at edges of each step plus marking of handrail New York City Local Law 26 for existing buildings (without the handrail marked)
E Continuous 25-mm marking across each step plus marking of handrail New York City requirement for new buildings
G L-shaped marking and 50-mm marking across each step plus marking of handrail Suggestion made by New York City, Department of Buildings (responsible for reviewing current PLM installations in NYC buildings)

The results showed that:

  • Stairwell E was the most appreciated by occupants for its clear identification of each step; this stairwell also obtained the most positive response in terms of comfort and safety.
  • Stairwell G also obtained good ratings, but because it uses more than twice the amount of material, it is a less attractive option from a financial point of view.
  • In terms of density and speed of movement, the behaviour of the evacuating occupants was similar in all four stairwells: in all cases, the crowd was dense and evacuation was slow.
  • Neither the PLM nor the reduced lighting appeared to play a role in the speed of movement.
  • The use of the handrail by over 80% of the evacuees confirmed the value of the team decision to mark the handrails with PLM.
  • Visibility of the landing and mid-landing location was a problem for some occupants in all of the stairwells. Ways to solve this problem are now being discussed.
  • Based on the study results, the team is now developing a guide for the installation of PLM wayguidance systems for all federal office buildings.

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