Emergency exits hard to find
By Anne Berit Bjørken
Photo: Jens Søraa
Every third person was unable to find the emergency exit.
Traditional "EXIT" signs are not effective in evacuating people from fires; this was one of the results of a wide-ranging series of evacuation trials that SINTEF has carried out.
The best type of marking consisted of illuminated strips along the floor. With the aid of such strips, virtually all (95%) of the human guinea pigs found the emergency exit.
The evacuation trials were one result of the debate that took place following the fire on board the ferry Scandinavian Star in 1990, in which 158 people died. It was claimed that it was impossible to see the signs in the corridors when these were full of smoke. Some people suggested that the solution would have been to make the lighting in the signs brighter.
"More detailed studies revealed that there was no convincing documentation that showed how emergency exits ought to be marked. This led to the Research Council of Norway´s programme for fires, explosions and major disasters taking the initiative for a study that would test a number of different marking methods. That was the basis of this programme," says Truls Paulsen, a researcher at SINTEF Safety and Reliability.
Railings
The evacuation trials in Trondheim also showed that safety railings with notches cut in them to indicate the direction to move in resulted in safe but slow evacuations. Everyone got out in this trial, but the evacuation took longer than using light strips along the floor. The tests took place in thick smoke, and under all three conditions the subjects could take as long as they wanted."Continuous marks along the floor or the walls of the corridor are the best way of getting most people out most rapidly. But at present, this type of marking is not even mentioned in the brochure on emergency lighting that the building regulations refer to," says Truls Paulsen.
"The tests showed that the standard signs that point to the emergency exits are difficult to see and interpret. We know that many of the subjects saw the signs, but could not understand them properly. It was disturbing to realise that so many people managed to make a mess of the evacuation process in spite of the fact that they know that they were taking part in an experiment, and that the corridor we had built up was relatively simple in comparison with many hotel or ship corridors," says Paulsen.
He believes that this means that current evacuation systems on board ships and in hotels and shopping centres are not good enough, and that the building regulations must be changed in order to make evacuations safer.
Scandinavian Star
The tests were carried out at SINTEF NBL - Norwegian Fire Research Laboratory, where a section consisting of a number of corridors was built. The evacuation route that the subjects followed was 30 metres long. A number of doors and exits with steps were set into the corridors. Various types of signs and lighting systems were then tested on 200 experimental subjects who were asked to pass through the smoke-filled evacuation route."Only five of the subjects experienced such serious problems with the smoke that they had to give up the tests. The first test was of traditional signs with lighting that showed the emergency exit. Visibility was poor because of the thick smoke. Just under 40% made different types of mistakes, and could not find the emergency exit. They either passed it, or tried to get out through the wrong door, and some turned round on the way out," says Paulsen.
"A surprisingly large number of people made serious mistakes. Traditional signs give us little support when we are in motion. They just tell us something about the direction to take, but nothing about walls, floors, corners or steps. These are all very important when we are trying to make our way in poor visibility," says Paulsen.
Marking lines
Other trials tested various types of marking systems that consisted of illuminated lines along the floor, as used in may aircraft. This type of marking resulted in the most rapid and efficient evacuations. The subjects who managed to find the emergency exit took only half as long using this method as when they followed the traditional system with signs at ceiling level. As many as 95% found the exit.Safety railings that let people feel the correct direction to move in also helped most people find their way to the exit. The weakness of this system was that the subjects took a long time to reach the exit. However, in combination with lights, the railings resulted in rapid, safe evacuations.
"The time taken for evacuation is critical. The results were therefore analysed in terms of critical time, which was set at 112 seconds. Anyone who was not out by then was regarded as having "died" of smoke inhalation," says Paulsen.
The marking line system was the only one that got everyone out of the corridors within the time limit. When traditional signs were used, 33% did not get out, and with the safety railings, 26% were declared "dead".
Researcher Truls Paulsen at SINTEF has conducted an experiment which showed that during a fire people are not able to find and follow the traditional EXIT signs.
Viewing distance and luminance
Previous research has shown that signs with high luminance are most visible in smoke. For this reason, many people have come to the conclusion that raising luminance levels is the best way of solving the problem of visibility in smoke. But they forget the significance of viewing distance on visibility. It is easy to demonstrate that a much better strategy is to reduce the viewing distance to the information than to increase brightness.Paulsen believes that Norwegian building regulation requirements for fire evacuation systems are not appropriate for fires that produce smoke, only for power cuts. According to the building regulations, exit signs in hotels must be visible at a distance of 30 m. Even a slight build-up of smoke makes it impossible to see signs at such a distance.
"The results of our tests and of a study of the literature show that Norway has adopted the wrong strategy for emergency lighting. We have stared ourselves blind on lux-values and battery packs, while important factors such as human behaviour, realistic evacuation procedures with smoke, and experience gained in real fires are all ignored," says Paulsen.
It is well documented that alarms and sprinkler systems have saved lives. It has turned out to be impossible to find similar examples of the value of emergency lighting.
"However, we do know that emergency lighting and marking signs do not help to distribute people among the evacuation routes available. People try to get out the same way as they came in, and this can easily cause crowding. Our suspicion that signs do not live up to expectations has been reinforced by a major study that showed that only 8% of the people noticed signs when they were fleeing from a fire."
SINTEF Safety and Reliability will continue to do research on this topic. In the course of 1993 - 94, for example, they will test various types of personal smoke protection equipment during evacuations from smoke-filled areas.
SINTEF is collaborating with a German company on the development of a program that can simulate how people behave when they are being evacuated from a fire.