The more occupied levels a building has, the greater the chance its evacuation won’t go as planned. In fact, the upper floors of a high rise are usually the last place to be during a full scale evacuation. Yet, full scale evacuations aren’t as common as we might think; often, only a few floors, or perhaps even as single floor, are evacuated due to fire, flooding, or a power outage; a fact that leads some building owners to neglect the safety of their high rises’ vertical exit enclosures, the long stairwells that no one uses until an emergency strikes.
In the U.S., the International Building Code (IBC), which has been adopted by all 50 states, and the International Fire Code (IFC), which has been adopted by at least 42 states, regulate the egress safety of vertical exit enclosures. The IBC applies new construction that features occupancy above 75 feet from the lowest level of fire vehicle access, while the IFC applies to new and existing construction that features the same type of occupancy. To make vertical exit enclosures evacuation safe, the codes require the following implements: hallway exit signs, luminescent floor identification signs, and luminescent (i.e. photoluminescent) egress markings.
Guidelines for Markings and their Application
To understand what egress stripes within a high rise’s vertical exit enclosures look like, it helps to describe their design and application. According to the codes, high rise egress markings should be luminescent and at least 1 inch in width. They are applied to the following elements within exit enclosures: handrails and handrail extensions, the leading edges of stairs and landings, the perimeter of landing areas, potential egress path obstacles, and the doorframes and hardware of exit leading doors. As this description shows, luminescent markings effectively reveal an enclosure’s elements and dimensions, an accomplishment that its alternative, emergency backup lighting, often doesn’t.
The Dangers of Backup Lighting
Emergency back up lighting poses two potential dangers to low visibility evacuations: it could fail (as happened during the 1993 World Trade Center bombing), and it performs poorly when smoke is present, it’s radiance reflecting off smoke particles instead of illuminating the enclosure. Electricity-free, luminescent striping, on the other hand, radiates an electromagnetic glow that remains visible through smoke, discouraging congestion that results from confused evacuees. Yet, there’s a difference between discouraging an egress pile up and expediting evacuations. Does the striping really do the latter?
While evacuation studies remain divided on this question, with some finding that the markings bring greater expedience than backup lighting and others that backup lighting has an similar effect, the stripes do have a more positive impact on evacuees’ sense of confidence and decision making ability, the primary predictors of an evacuation’s expedience or lack thereof. By keeping an enclosure’s dimensions and equipment visible at all times, luminescent striping decreases evacuees’ sense of panic and indecision, thereby supporting expedient evacuations.