By Zoe Naylor
As buildings get taller and cities reach further up to the sky, the need for slick evacuation procedures is paramount. For the past thirty years, the message has been to avoid using elevators in the event of a fire; but, as CW finds out, there is growing support to move back inside those sliding doors.
|~|98prod200.gif|~|Some designers are looking at the possibility of developing fire-proof elevators, which can be used to evacuate tall buildings in the event of a blaze.|~|For more than three decades, the message from the elevator industry to the public has been very clear: Do not use a building’s elevators in the event of a fire.
But the 2001 collapse of the Twin Towers in New York prompted a re-examination of the way escape systems are designed the world over — particularly for tall buildings — and has been the impetus for research into finding ways in which elevator-assisted escape can be provided safely.
There are a number of reasons why concerns have been voiced over the adequacy of relying solely on stairs to move large numbers of people from significant heights.
Buildings around the world are getting taller. With the recent announcement of super-tall developments to be constructed in Dubai, the need for elevator escape has become a pressing issue.
“The question is, can the elevators that normally provide vertical transportation be designed to supplement the stairways by providing an additional safe exit route during fires,” says Vinay Deshpande, operations manager at Locke Carey Fire Safety Consultancy in Dubai.
Secondly, using elevators during a fire could be a practical way to evacuate occupants with disabilities, provided that the elevators can be used safely.
The construction industry generally recognises the use of elevators for fire department access and operations, and to some extent accepts the use of the elevators as a possible means of escape for people with disabilities.
According to Deshpande, the current practice is that in the event of fire, the elevators are taken out of service and people are advised not to use them. While this policy does not generally represent a severe hardship for most buildings and occupants, it does present difficulties for people with disabilities and for tall buildings, where stairway escape times can be considerably extended.
Thirdly, the past assumption that an entire building doesn’t need to be evacuated all at once is being re-examined after the events of 9-11. The current design practices of escape systems reflect the assumptions that tall buildings will be evacuated by partial or phased evacuation procedures, and only fully evacuated as a last resort.
A report published earlier this year by the National Institute of Standards and Technology in the US suggested that approximately 3000 people were able to evacuate the second World Trade Centre tower, because they used elevators in the 16 minutes before the second tower was hit.
If buildings are designed for simultaneous evacuation under current escape design practices, there will be a natural height beyond which the stairs would occupy such a large portion of the floor area that such buildings would be impractical to design and construct.
According to Deshpande, there are vital issues concerning elevator use in the case of fire emergencies that must be taken into consideration: “Equipment reliability, communication, control, human behaviour and operational procedures all need to be addressed before this mode of vertical transportation can be implemented.”
In terms of technology, for an elevator to be used during a fire, it must be able to withstand the typical problems associated with the heat, smoke and water from a blaze.
Today’s elevators are designed to operate on the outside of
buildings, hence water-tolerant technology is available and
already in use.
Emergency power for the elevators is another consideration. Under codes of practice in many countries, this prerequisite is already met with elevators that are used for fire fighting-purposes.
Another area to look at is enclosed lobbies, which should be provided on each floor of the building to help protect occupants from a fire while awaiting the elevator. These will also serve as an area of refuge for people with disabilities.
The elevator should be installed in a smoke-proof shaft, built to a required fire resistance as per the respective building codes. “It should also be pressurised against smoke infiltration to prevent smoke and heat from moving through the building via the shafts,” says Deshpande.
Pressurising the elevator lobby as well would protect the area from smoke and help minimise pressure differences across the hoist way door that can jam the door mechanism.
A vital element is the pooling of knowledge from various sources: “Fire engineers and elevator designers will need to work closely to develop adequate safeguards to enable an elevator to be easily integrated into the building, with the assistance of building designers,” says Deshpande.
Previous and ongoing research by fire engineers — combined with recent technical advances — may be able to address the technology issues generally identified as being critical to the safe and reliable operation of elevators during fires.
But according to Deshpande, another vital consideration is how to develop operating procedures that are sensitive to human factors. “The operational procedures for escape elevators raises a variety of issues,” he explains.
“The present practice of cautioning the public against the use of elevators in the event of fire could severely lessen the occupant’s confidence in the elevator system in case of fire emergency.” This may lead to occupants becoming impatient and overcrowding the elevator, which can cause the car to stop functioning and remain at the floor indefinitely.
He believes there is a fundamental lack of understanding of human use of elevators during emergencies — the amount of time occupants will wait at an elevator is unknown.
“Without proper preparation and training, occupants may become fearful of the dangerous conditions and decide to use the stairs,” he says. But if a building is designed for a certain distribution of occupants between the stairs and the elevators, then this could cause congestion in the stairway.
There are many factors — of both a technical and human nature — that need to be addressed before elevators can be advocated as a safe means of escape from a building during a fire.
But according to Deshpande, if all these issues can be
satisfactorily dealt with, there seems to be no logical argument against using elevators for escape in tall buildings.||**||