The 1st terrorist bomb attack at the New York City World Trade Center in 1993 disabled the WTC’s main electrical power line and knocked out the emergency lighting. Smoke generated rose up to the 93rd floor of both WTC towers, even in the emergency staircases. It took WTC occupants hours to evacuate, many through the smoke. Following these events, the Port Authority of New York and New Jersey installed PERMALIGHT® photoluminescent exit path markings on each step edge, each landing and the handrails inside the emergency staircases.
Seven years later when 9/11/2001 happened, these glow markings came to good use. NIST (National Institute for Standards and Technology) interviewed survivors of the 9/11 events and 33% of people in Tower 1 and 17% of people in Tower 2 mentioned the yellowish markings that aided their escape. Based on the NIST recommendations, the City of New York soon implemented a range of new requirements after 9/11, including photoluminescent exit path markings in high-rise office building emergency staircases.
Since its 2009 edition, NFPA (National Fire Protection Association) has non-electrical exit stair path marking requirements in Chapter 7: Means of Egress. Also in 2009, ICC (International Code Council) added non-electrical, luminous egress path marking requirements for high-rise building staircases to its nationwide codes IBC (International Building Code) and IFC (International Fire Code). The markings are required in buildings of groups A – assembly, B – business, E – educational, I – institutional, M – mercantile and R-1 – hotel/motel. The markings get applied to each leading edge of a landing and on each step inside a staircase. The top surface of all handrails gets marked. Low-location perimeter demarcation lines mark the egress path along all horizontal areas, i.e. on landings along the wall base (no more than 4 inches above the floor) and in any vestibules/ corridors that are part of the egress path. Obstacles that project more than 4 inches into the egress path (such as pipes, evac chair cabinets, fire hoses) get highlighted with obstacle warning marking to avoid people bumping into a protrusion in the dark. Floor identification signs illuminate the stairway information. Door frames, door handles and push-bars of doors from exit enclosures through which occupants must pass in order to complete their evacuation get marked plus an emergency exit symbol sign (Man to the left or right) gets installed no higher than 18 inches above the floor. Find further details here: IBC IFC compliant Egress Path Markings
The photoluminescent egress path markings are installed in low-location to be visible underneath the smoke layer. During a building fire typically smoke forms, rises under the ceiling and obscures the electrical lighting. Occupants shall drop to the floor where breathable air remains the longest and evacuate under the smoke layer. Down there, the photoluminescent floor proximity egress path markings are installed.
The photoluminescent egress path markings are NON-electrical, so they work during power outages. Photoluminescent markings are typically UL1994-listed by an NRTL (Nationally Recognized Testing Laboratory) like Underwriters Laboratories or ETL Intertek Testing. The markings get activated by only 1 foot-candle of ambient lighting and – just like electrical emergency lighting – get tested at 90 minutes in the dark by the NRTL to earn the prestigious UL-listing or ETL-listing. The photoluminescent signs and markings then continue to emit their glow for hours to come until they get re-charged again by ambient lighting. Photoluminescent markings to be installed on the floor, such as metal stair nosing and anti-slip tape additionally has to get UL410-floor suitability tested.
The new One World Trade Center in New York City again got equipped with photoluminescent exit path markings in the emergency staircases to make the high-rise building safer with lights on and off. The circle of safety is completed. New York City Local Law 26 versus Local Law 141 Plus the building codes now require Photoluminescent Egress Path Markings in new high-rise construction hotel/motel, office/administrative and hospital for improved building occupants safety.