By Jonathan M. Rubes, P. Eng., Leber Rubes
Cover Story: Buildings: AftermathEngineering
It's hard to improve on perfection. The statement sounds ridiculous when the subject matter is high-rise fire safety. Nonetheless, to the best of my knowledge, there has never been a fire death in a s...
It’s hard to improve on perfection. The statement sounds ridiculous when the subject matter is high-rise fire safety. Nonetheless, to the best of my knowledge, there has never been a fire death in a sprinklered high-rise office building in Canada. From that point of view, a perfect record exists.
There is, however, also a saying: “This is a disaster waiting to happen.” Some might say that high-rise buildings are that disaster waiting to happen and that September 11 proves it.
A great deal of investigation is taking place regarding the performance of the World Trade Center after the terrorist attacks, but most early reports seem to be focusing on the structural aspects of the buildings, what contributed to their collapse and what can be learned. Unfortunately, the details of how the other fire protection systems performed and aspects of occupant behaviour are still anecdotal and not yet available in an accurate and reliable form.
This brings us to an interesting point — information. Fewer things are more frustrating than wanting a piece of information and not getting it. Is the plane on time? Why is the traffic not moving? Will it rain today? Why am I still on hold? And by the way, a plane just crashed into the building beside us, should we evacuate?
According to one press report, a survivor of the New York attack said that after the first plane crashed occupants of the second tower were told to remain in place as the problem was not in their tower. Now people are asking why. Had the people in the second tower been told to leave immediately, perhaps there would have been more survivors.
The fact is, the initial announcement was appropriate under the circumstances. The problem was in another building. There would be no way to know it was terrorism. There would be no way to know the crash would be repeated immediately in another building. There would be no expectation that a problem in one building would affect an adjacent building.
It is a mistake to suggest that a cautious approach would have been to instruct occupants to exit, “just in case.” Unnecessarily evacuating a 110-storey building could result in trip and fall accidents on stairs, heart attacks, anxiety attacks or other medical emergencies.
Exits are only designed to evacuate one floor at a time in an expedient way. The intent is to get occupants off the floor on which there is a fire and then, as required, off other floors. Evacuating everyone unnecessarily can be a problem if certain occupants from a floor who are in greater danger can’t leave because the exit stairs are filled with people from other floors that are not under immediate threat.
The initial communication to occupants of the second World Trade Center tower could therefore be considered appropriate. Unfortunately, it seems there were no subsequent announcements. Why? Simple. A jet plane full of fuel crashed into the building. Apparently, the ability to communicate and provide information to occupants was lost. Information was provided initially but could not be followed with more advice as it became necessary.
What systems can do
According to the latest design and technology of fire alarm systems, they can remain functional in the event of a serious fire or even most terrorist activities. Highlights of a recent Toronto high-rise fire alarm retrofit included the following:
Use of distributed system technology incorporating a number of transponders (data gathering panels or field panels) all operating in a peer-to-peer format. Each transponder, which serves four to six floors, communicates directly with every other transponder connected on the system network.
Network wiring for both the system communication and the paging buss between transponders runs in fire-rated separated spaces, or in a fire-rated cable assembly, to maintain operating integrity for a period of one hour. The network wiring is connected to the transponders in a “redundant” loop format which ensures that a fault in one location has virtually no effect on the system performance.
Multiple display command centres (DCC) are provided, each with full system annunciation, zoned voice communication paging and zoned control for emergency phones. One DCC is provided at the street entry in the Central Alarm Control Facility for use by the fire department, one in the building operations centre for use by the building operators, and there is a portable command centre. The portable command centre can be connected anywhere on the network and within a few minutes will provide full system control and annunciation.
A cellular telephone interface furnishes an input path to the voice paging system near the top of the building. The cell phone interface has the ability to provide voice paging to all circuits that remain connected to the network voice path. Access to this input is available only after giving a password and will only function when paging cannot be provided from any one of the primary DCCs.
With this design, even a terrorist attack on the building central alarm and control facility, would not render the system incapacitated, although it would lose some level of performance.
The operators would keep full control and operation of the system from either the second permanent DCC or the portable command centre.
In the case of the World Trade Center, it is likely that both the primary and the return path for the main system wiring were sheared at the floor of impact, separating the upper section of the building from the lower. With the loop redundant wiring format used in the Toronto building, all floors up to the floor of impact would continue to report to the DCC at the base, and alarm signaling and voice paging would continue to function for those floors. The floors above the impact would work as a group and provide alarm signaling from any alarms initiated in their domain. It also would still be possible to provide voice paging messages to the upper floors using a cell phone to provide input to the cell connection at the top of the building. Cellular technology allows almost anything to be done, although such systems have to be reliable day to day.
Given that systems like the one above and the one used in the World Trade Center can achieve exemplary performance under almost all reasonably expected circumstances, is there any real justification for going beyond their level of design?
Once you have a system capable of performing to an acceptable level, the important issue becomes maintaining and operating the system. First, it is imperative that the system is tested and maintained to ensure it will perform when called upon. Second, in order to provide the information people are looking for, someone has to know how to use the system and what to say. Even if details are not known, telling occupants that an investigation is taking place reassures them that someone is doing something.
Fire codes require that fire alarm systems are tested and maintained, and they also require that buildings have fire safety plans incorporating emergency procedures. Enforcing the requirements on an ongoing basis is difficult because the authorities don’t have the manpower to check all buildings continually. However, the codes make it the building owner’s responsibility to comply.
Thus, while a building might have the most sophisticated fire alarm and voice communication systems that enable it to perform at the highest level during a fire, whether the systems continue to work effectively depends on the attitude and efforts of building owners and operators. Without proper staff training, the benefits of the equipment are lost.
Nothing is perfect and no system is failsafe in our unpredictable world. Complying with the applicable codes and standards still would not have enabled operators to communicate with all the building occupants in the World Trade Center disaster. But code compliance would address reasonably expected circumstances in other high-rise buildings. With respect to fire alarm and voice communication systems, current codes don’t need substantial changes, but we do need to improve attitudes towa
rds system maintenance, testing and training.
Jonathan Rubes, P.Eng. is a principal in Leber/Rubes Inc., fire protection consultants of Toronto.
The photographs in this and the following article are by Jeroen Morrien of the Netherlands. Morrien was on vacation in New York on September 11. He was in the WTC south tower lobby about to buy a ticket for the observation deck when the north tower was hit. As he fled the area he met two businessmen on their way to take the New Jersey ferry and spent the day with them in an apartment watching and photographing the collapse of Manhattan.