IFC/IBC Approved High Rise Egress Markings: How do they Affect Evacuations?
IBC/IFC approved high rise egress markings feature two aspects of IBC/IFC compliance: luminescence and a minimum width of 1 inch. Otherwise, the effect of the markings depends on how you apply them, with the codes being precise about their application to the following elements within vertical exit enclosures: handrails and handrail extensions, the leading edges of stairs and landings, the perimeters of landing areas, potential egress path obstacles, and the door frames and hardware of exit leading doors.
Once applied to these elements, the markings reveal an enclosure whose dimensions are perceptible in the darkness, even with the addition of heavy smoke. That’s why they’ve become the preferred method—and in many places the mandated method—for ensuring visibility in vertical exit enclosures during low visibility evacuations, a movement that began after the bombing of the World Trade Center in 1993, where evacuees traversed dark stairwells after the bombs disabled the buildings’ emergency generators, disabling their back up lighting.
Backup Lighting was never a Good Solution
Even before 1993, back up lighting had revealed a weakness not associated with power failure: it performed poorly in the presence of smoke, becoming like a headlight in fog as smoke thickened, its incandescence reflecting off smoke particles instead of brightening its surroundings. But the ultimate goal of evacuations, especially those that involve fire, is expedience, a goal that depends on visibility but also other factors, particularly evacuee behavior.
The Problem of Panic
According to a recent study by researchers at the National Institute of Standards and Technology (NIST), most predictions by evacuations experts about evacuation time have been flawed thanks to an X factor that the five factors used by building engineers to assess egress in stairwells (pre-evacuation delay, distance traveled during evacuation, counterflow, stairwell geometry and density of evacuees in a stairwell) doesn’t accommodate: the behavior of evacuees, any of whom could trigger an event that changes evacuation time.
Assessing the behavior of evacuees brings the difficulty of assessing what people do when they—to use the term broadly—panic. Does someone create counterflow by attempting to retrieve something? Do people push and shove, creating egress jams? It’s often hard to say, making it hard to come up with a foolproof method for fast evacuations. So where do luminescent egress markings fit in this scenario? Ostensibly, they deter egress jams by clearly outlining evacuees’ surroundings; an effect that could be strengthened with the presence of luminescent IBC and IFC approved exit signs, floor identification signs, and emergency exit symbols.
Concerning research on the markings themselves, some studies have found that they improve evacuation time when smoke is present, and others that backup lighting works just as well. However, you can always be sure that luminescent markings will lead to speedier, safer evacuations than failed backup lighting.