Supply and Demand: The push to understand building energy use | EXPLORE→

How 9/11 Changed Elevator Evacuation Technology and High-Rise Safety

It’s an understatement to say the harrowing events of the 9/11 attacks changed the world in ways still felt today. Most Americans remember exactly where they were when they heard the news, and most of them were glued to their TV screens for hours that fateful day. Now a growing share of Americans have no memory of the event, too young or not yet born, and have no recollection of the world before heightened airport security and “if you see something, say something.” 

The 9/11 attacks have impacted many parts of our society, but one lesser-known effect has been on building engineering. In the aftermath of the attacks, a federal investigation of the World Trade Center’s evacuation led to high-rise building code changes seeking to make evacuations safer. One of these changes has been a change in the way we think about emergency evacuation elevators.

Never forget

It’s estimated that between 2,146 and 2,163 people were killed in the World Trade Center towers on 9/11. The majority were killed in the north tower, the one that was struck first, according to the U.S. National Institute of Standards and Technology (NIST) investigation. Sixteen percent of people who escaped the south tower, the second to be attacked, were able to evacuate via elevators during the sixteen minutes between the two impacts. 

Researchers simulated a hypothetical attack where elevators weren’t available and determined elevator use saved about 3,000 lives in the south tower alone. The NIST’s report went on to make several recommendations to high-rise building safety protocols that were eventually adopted into building codes, including the International Building Code (IBC).

Changes to the IBC code include widening emergency stairwells in high-rises and requiring glow-in-the-dark markings on each stair. But perhaps the biggest code change prompted by 9/11 is a voluntary recommendation for installing emergency evacuation elevators in buildings more than 420 feet tall. This change to the elevator code offers a much easier evacuation method for people unable to use the stairs, such as the elderly or disabled. The adoption of emergency elevators in the code was likely triggered by a major problem in evacuations during the 9/11 attacks: excessive crowding in the World Trade Center staircases. Code specialists believe emergency elevators can lead to much faster and more efficient evacuations in skyscrapers and high-rise buildings that are often several stories high.

Volunteers wanted

All elevators designed for evacuation in high-rise buildings must comply with special provisions required by Section 3008 of the International Building Code. While these types of elevators offer a new safety design feature for architects and building planners, they’re not a mandatory requirement (yet). Emergency evacuation elevators can be used for buildings of any height, but they’re typically installed in skyscrapers and high-rises. 

One of the benefits of installing these emergency elevators is that the additional interior exit stairway width required by IBC can be removed. Buildings that house permanent residents, though, are exempted from that caveat. The use of evacuation elevators is still very much in its infancy, and there are very few of them installed in high-rises across the U.S. and worldwide. But as buildings grow taller, the benefits of emergency elevators mean many experts believe the technology will catch on. The IBC didn’t incorporate evacuation elevator procedures into its code until 2012, followed by the ASME A17.1/CSA B44 elevator code in 2013.

“Each state and even some cities regulate when they adopt these building codes,” said Phil Hampton, Chief Engineer and Director of Codes, Standards and Sustainability for TK Elevator. “The process of writing code and later adopting those codes can take many, many years. So, I think we’ll continue to see over the next 10 years a lot of growth in this type of technology and possibly see it expand to other types of buildings.”

The benefits of evacuation elevators in high-rise buildings are obvious, the primary one being easier egress that would typically require descending several flights of stairs. If a fire starts on the 75th floor, taking the elevator is a much better evacuation route, especially with people with mobility problems who can slow down movement in a crowded stairwell. 

First responders

Emergency elevators are created with emergency scenarios in mind. They have safeguards that protect against water, smoke, and heat intrusion into the hoistway shaft, and they can run on backup power in case of an outage. Often times they are equipped with systems that provide audible instructions and can be programmed to automatically take occupants to a specific ‘fire floor.’ 

Perhaps the most challenging aspect of evacuating occupants via elevators is the training and communication involved. For decades, people have been told to not use elevators during emergencies and fires. So, jumping on an elevator when the alarms are going off is a big culture change. Hampton said training and emergency drills are crucial because of this, and the plethora of audible and visual communication directing occupants helps, too. Still, emergency elevators are a rarity today, even if Hampton predicts their use will grow. His company, TK Elevator, installed North America’s first emergency evacuation elevator system in 2017 in San Francisco’s 181 Fremont Building. Fourteen of the 17 elevators in the 802-foot-tall mixed-use building have Occupant Evacuation Operation functionality. Because the elevators were the first of their kind in North America, the most challenging part of the installation was the “extensive testing and sign-off from various government agencies, as well as the fire department,” said Jake Albini, Director of Real Estate at Jay Paul, the owners of the Fremont Building. Nobody had tested the technology before, though TK Elevator and Jay Paul eventually gained all approvals.

“The building owners weren’t required to install the emergency elevators, and I would say they were ahead of their time,” Hampton said.

The new Bank of America Tower in Charlotte is one of a small handful of buildings worldwide to install emergency elevator systems. Schindler Elevator designed the systems for that building, and Charlotte Fire Department Captain Jackie Gilmore told WCNC she’s heard positive comments about the elevators from firefighters who have responded to the building. Gilmore said the system enables firefighters to more quickly perform critical tasks instead of rushing up and down high-rise stairs to ensure safe evacuations.You might think that one of the impacts of 9/11 would be fewer ‘super-tall’ buildings being constructed, but you would be wrong. The past two decades have seen a huge increase in the number of tall buildings, the average height of the 100 tallest buildings in the world has increased 41 percent since 2001 from 932 feet to 1,309 feet, according to a report by the Council on Tall Buildings & Urban Habitat. These super-tall buildings aren’t just luxury high-rises, either, they’re offices, hotels, and even shopping centers. With this growth of skyscrapers and high-rises, emergency elevators could be an attractive and maybe even necessary building technology. Going forward fewer and fewer will remember that aweful day but they will hopefully be much safer thanks to the lessons learned from the tragedy.

Image - Design