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Some safety experts are rethinking some advice that you find in almost any elevator. The sign on many elevators shows flames and a stick figure running down a stairway. The sign says in case of fire, use stairs. It turns out that may not be the best idea in every case.
NPR's Nell Greenfieldboyce reports there's growing interest in elevators that are fireproof.
NELL GREENFIELDBOYCE: The Stratosphere Tower in Las Vegas is over 900 feet high. It's the tallest building west of the Mississippi. And at the top, it has the highest thrill rides in the world. Here's one other unexpected ride: if there's a fire, people will flee in the elevators.
Unidentified Man: These elevators travel at the speed of 1,800 feet per minute. Each level of the cab can accommodate 13 people.
GREENFIELDBOYCE: This video, put out by the local fire department, says the elevators are way faster than walking down over 1,600 steps. Officials note that relying on elevators for evacuation is unusual. But Richard Bukowski says that's starting to change.
Mr. RICHARD BUKOWSKI (National Institute of Standards and Technology): I can't find a building that's currently under construction or planned anywhere in the world over a thousand feet that isn't using protected elevators.
GREENFIELDBOYCE: Bukowski works on building-safety issues at the National Institute of Standards and Technology. That's a federal research agency. He says people thought 9/11 would mean the end of mega high rises.
Mr. BUKOWSKI: And in fact, it's been the other way. There are very tall buildings being built.
GREENFIELDBOYCE: Bukowski says the main effect of 9/11 is that developers realized they needed better ways to evacuate these buildings. Elevators have started to look very appealing, and that's a huge change. For decades, experts have warned people that elevators could be death traps.
Edward Donoghue works for a trade group called the National Elevator Industry. He says that advice came after some tragedies back in the 1960s and '70s. Elevators accidentally took people to floors that were burning.
Mr. ED DONOGHUE (National Elevator Industry): The elevators came down and responded to what they thought was somebody pressing a call at that floor. The doors opened up and that's what led to the fatalities inside the elevator cars.
GREENFIELDBOYCE: Elevators were redesigned. Little signs went up telling people to use the stairs. And now if smoke or fire gets anywhere near lobbies or the guts of the elevator system, the cars go to the ground floor and wait.
Mr. DONOGHUE: People can stand there all day long and push the button and the elevator will never respond because it's been taken away from them.
GREENFIELDBOYCE: But in the last few years experts have started to realize that stairs have their own problems.
Mr. JAKE PAULS (Building Safety Analyst): If we talk about stairs, we're opening Pandora's box, so to speak.
GREENFIELDBOYCE: Jake Pauls is a consultant in Maryland who spent decades studying how to evacuate buildings. He says disabled people can't take the stairs, and in tall buildings stairs can get jam-packed with people.
Mr. PAULS: They won't be able to move at the top and they'll just dribble out the bottom.
GREENFIELDBOYCE: At a rate of about one person a second.
Mr. PAULS: One person a second is a pretty slow rate when you have 10,000 people trying to get down a stair of a very large building.
GREENFIELDBOYCE: Plus, he says, Americans are getting fatter, less fit, and just slower at getting downstairs.
Mr. PAULS: So elevators are starting to look better. For example, you could evacuate a very high rise office building in something like 30 minutes using elevators alone. That same building might take an hour or two, maybe even longer, to evacuate by stairs.
GREENFIELDBOYCE: For evacuation elevators to work, they have to be protected from heat, smoke and water, and that's technically doable. For example, you can keep smoke out by pressurizing the elevator shaft. If the sprinklers go off, sloping floors and drains can keep water away. And elevator lobbies can be redesigned to create refuges where people can wait.
Starting this year, San Francisco will require certain kinds of tall buildings to have at least one protected elevator. Barbara Schultheis is the city's fire marshal. She says this measure was intended to help firefighters, not necessarily residents who are trying to escape.
Ms. BARBARA SCHULTHEIS (Fire Marshal): We haven't gone the route of self evacuation yet. And it's my belief that further study is needed before we would go that route.
GREENFIELDBOYCE: Further study into questions like this one.
Ms. SCHULTHEIS: How do you reeducate people to use elevators when they've always been taught not to use the elevators?
GREENFIELDBOYCE: Especially if the elevators in some buildings are protected and others aren't. Richard Bukowski says confusion could become a real issue if protected elevators become more common.
Mr. BUKOWSKI: The signs that say don't use the elevator in case of fire will go away. But we also need something positive there, some kind of international symbol, if you will, for a fire-safe elevator.
GREENFIELDBOYCE: And he says if people aren't convinced, they'll always be able to take the stairs.
Nell Greenfieldboyce, NPR News.