Author(s): Angelo Verzoni. Published on July 1, 2017.

Fast, Safe, Essential

The argument for occupant evacuation elevators

INTERVIEW CONDUCTED BY ANGELO VERZONI

When airplanes hijacked by terrorists smashed into the World Trade Center in New York City on September 11, 2001, an estimated 17,400 people scrambled to evacuate the skyscrapers. Most of them took the stairs. Survivor accounts describe the buildings’ stairwells as crammed with occupants trying to descend and first responders trying to go up, which slowed evacuation. There were stories of smoke in the stairwells, and water from severed pipes cascading down the steps. Within two hours, both buildings crumbled to the ground. Nearly 3,000 people died.

The terrorist attacks of 9/11 illustrate what can go wrong when a large number of building occupants rush to the stairs to get out, especially in skyscrapers. If more people had used the elevators, would more people have survived? It’s hard to say, since stories from 9/11 also suggest stalled elevators contributed to more deaths, and elevator shafts funneled jet fuel down to lower levels and smoke throughout the buildings. But 9/11 did renew the conversation—a conversation that began in the aftermath of the Triangle factory fire in 1911—about how to safely evacuate building occupants using elevators in addition to stairs.

For almost as long as elevators have existed, we’ve been conditioned to avoid them in the event of fires and other emergencies. Now, as elevator technology progresses and occupant evacuation elevators, or OEEs, emerge, that notion is slowly changing. For the most part, OEEs don’t look any different than regular passenger elevators, but they’re designed to be used in fires or other emergencies to evacuate building occupants, as well as for everyday use. It’s an almost inevitable evolution as buildings become taller at a rapid pace. Currently, the tallest building in the world is the Burj Khalifa in Dubai, which stands at more than 2,700 feet tall—more than 1,000 feet taller than the original World Trade Center towers. Jeddah Tower, a building under construction in Saudi Arabia, is slated to dwarf the Burj Khalifa by about 600 feet.

While proponents say the need for occupant evacuation elevators is clear, fire and life safety officials remain wary. This was evident in June when Sagiv Weiss-Ishai, a fire protection engineer with the San Francisco Fire Department, gave a presentation on OEEs at the NFPA Conference & Expo in Boston. (Weiss-Ishai serves on the Protected Premises Fire Alarm and Signaling Systems technical committee for NFPA 72®, National Fire Alarm and Signaling Code, and is also a member of the OEE Task Group on NFPA 72, Section 21.6.) His talk drew dozens, some of whom squirmed in their chairs and barraged him with questions throughout the 90-minute presentation. By this fall, San Francisco will become the first city in the United States to have an OEE that incorporates what’s known as an OEO, or occupant evacuation operation, as defined by American Society of Mechanical Engineers (ASME) A17.1/CSA B44, Safety Code for Elevators and Escalators.

An OEO is the specific elevator system operation that tells OEEs where to go and when in order to safely evacuate people in a fire or another emergency. Elevator systems in a handful of skyscrapers around the world—including the Burj Khalifa and One World Trade Center, which now stands near the site of the original towers in Lower Manhattan—incorporate some of the attributes of OEEs but stop short of having the OEO function. Currently, OEEs provided per the International Building Code (IBC) Section 3008 must incorporate an OEO.

NFPA Journal spoke with Weiss-Ishai after his C&E presentation to ask him about how evacuation elevators work, why they’re needed, and how he sees the technology developing.

Why is it considered unsafe to take a regular elevator in a fire?

It’s unsafe to take a regular elevator for many reasons. If you have a fire in the building and somebody’s trying to take the elevator, they might take it to the fire floor. Some people die from this. The heat of the fire can melt the buttons you press to call for an elevator at the elevator landing, shorting the contact, and it’s like somebody’s pushing it so the elevator goes to the fire floor. There are many more reasons, but that’s the essence of it. They’re not safe. They’re not designed to be used in a fire.

What have people with mobility issues traditionally done?

Typically, in buildings that don’t have evacuation elevators, there are two possibilities. If the elevator is still in normal service because there’s not enough smoke in the lobby to recall, or shut down the elevator system, a person in a wheelchair or with mobility issues would have to make a decision. If the person feels safe enough, if they don’t smell fire or see smoke and there are areas of refuge on each floor in the stairs or the elevator lobby, the person can move horizontally to these areas. Areas of refuge are designed with smoke barriers and communication systems that allow the person to call and say, “I’m here. Come get me.” But if the person sees fire or smells smoke, they can choose to take the elevator to escape, assuming the elevator is still operating in normal service. It’s not safe. But what’s more unsafe, taking the elevator or waiting for the fire to get to you?

Is that one of the reasons OEEs are needed?

The main reason OEEs are a good thing in my opinion is that they provide means for people who have mobility issues to get out during emergencies. It can be older people or small children, it can be people in wheelchairs, it can be pregnant women, it can be someone with a bad leg, or anyone else on higher floors in a high-rise building. It can drastically reduce the time of evacuation in very tall buildings if the elevators are used to evacuate occupants in addition to the stairs.

For people who don’t have mobility issues, what are the problems that arise from stair evacuation?

In an office building, for example, you can have a very large occupant load. You can have 500 people on a floor. If you evacuate five or six floors, that’s thousands of people getting into the stairs, which become overcrowded. Firefighters are using the stairs, too. If you have evacuation elevators, it’s much faster.

What makes OEEs different from regular elevators?

In general terms, it’s the building protection features around the elevators—fire walls, protection from water, heat, and smoke, pressurizing the lobbies, pressurizing the stairs, and preventing any bad things from getting into the elevator systems. Even if there’s a fire in the building, the OEE system is designed to prevent the fire and smoke from getting into the elevator lobby or into the elevator hoistway. The OEEs also can run on backup power, so if you lose the power to the building, a very large emergency generator is provided and can operate all the passenger elevators simultaneously.

How does occupant evacuation operation, or OEO, work with an OEE system?

OEO is how the elevator system is designed per the ASME Safety Code for Elevators and Escalators to automatically perform a partial or total building evacuation without somebody pushing a button or telling the elevators what to do. That’s the complicated electronic program, or computer system, that tasks the elevators to go to specific floors automatically. It prioritizes where the elevator goes, and when, based on inputs from the building fire alarm system specified in NFPA 72. Three buildings under construction in San Francisco will be the first in the U.S. with complete ASME-compliant OEO. Based on my understanding, New York City and Seattle are also looking at this.

What’s the history behind OEEs?

While the use of elevators during a fire event has been discussed in one form or another for more than 100 years, the concept was revisited in earnest in 2002 following some of the preliminary work on the World Trade Center study from FEMA and NIST. After September 11, a number of task groups formed to talk about how to evacuate tall buildings. At first, the thinking was that we needed more stairs. The IBC was changed to require that buildings more than 420 feet tall have an additional stair beyond what the IBC would normally mandate. Then came the concept of the evacuation elevator, which originally was supposed to be in addition to the extra stairs. The way the IBC is currently written, OEEs can be used in lieu of the additional stair so long as the other stairs provide the egress capacity needed for the building.

What’s your take on that arrangement?

I don’t like it, personally. I want the additional stairs. Stairs are passive systems—there is no smartness to it, there’s nothing that can fail. For economic reasons, though, it may be tempting for owners and architects to use the OEE exception in the IBC code in lieu of an additional stair. Stairs can take up to 250 square feet of area on each floor. Multiply that by 100 floors in a high-rise building, and that’s a lot of premium real estate not utilized as rentable space.

How are OEEs addressed in NFPA codes?

Both NFPA 101 and NFPA 5000 have a section on OEEs. The codes provide the design and operational criteria. No egress credit is given for the OEE and there are no requirements to provide an extra stair if the OEE isn’t provided. NFPA 72 Section 21.6 has contained information on occupant evacuation elevators since the 2010 edition. It’s been completely revised since then. We proposed a whole new section based on many hours of task group work. If the second draft is passed in July, it’ll be included in the 2019 edition of NFPA 72 subject to the membership vote next June.

What does the revision aim to accomplish?

It’s basically to make it more consistent with the ASME code for elevators, so there are no inconsistencies between NFPA 72 and ASME. Many of the proposed revisions to NFPA 72 are based on the real-life experiences from one of the San Francisco projects and also on the ASME task group work for OEO.

Do you think OEEs will become more common in the future?

Yes. Right now, all kinds of new technologies and innovations are being developed for elevators. More are coming all the time. We can’t stop the vertical transportation technology from developing, so we have to ensure as much as we can the safety of these elevators. That’s what we’re trying to do with all the fire and elevator safety codes: make sure that if something happens, building occupants and firefighters can use elevators safely. As cities become overcrowded and people build these towers, they’re going to try to condense as much usable space in them as possible, and they will try to push OEEs into many of these new towers.

During your C&E talk, audience members had a lot of questions. Some of them seemed like they didn’t have faith in OEEs. Is there a lot of concern out there?

It’s scary. Nobody’s done a complete OEE system before. We’re going to make sure it does what it’s supposed to do. Hopefully we never have to use it. It’s basically the concept of replacing a passive system like stairs with a very, very complicated, computerized, mechanical, electronic system, so a lot of things can fail. If you have an earthquake, for example, and the building shakes, it might put all the elevators out of service at the same time. Now what do you do? We’re doing all this analysis assuming everything works with no problems. People are worried about this. That’s why I think having occupant evacuation elevators as additions to, not in lieu of, an extra stair is the right thing to do. It’d make me feel a lot better.

ANGELO VERZONI is staff writer for NFPA Journal. Top Photograph: IStockPhoto