THE EFFECTS OF SMOKE ON PEOPLE S WALKING SPEEDS USING OVERHEAD LIGHTING AND WAYGUIDANCE PROVISION

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1 THE EFFECTS OF SMOKE ON PEOPLE S WALKING SPEEDS USING OVERHEAD LIGHTING AND WAYGUIDANCE PROVISION M S Wright, G K Cook and G M B Webber Research Group for Inclusive Environments, The Department of Construction Management & Engineering, The University of Reading, Reading, Berkshire. RG6 6AW, UK This paper presents results from 18 people who have passed through a smoke filled building under six types of emergency lighting. Their walking speeds are analysed to show which lighting systems allow people to walk along the route most quickly. It is shown that high mounted lighting that is similar to that called for by British Standard 5266 causes people to walk significantly slower than the tested wayguidance systems. Normal overhead lighting also causes people to walk more slowly than some of the wayguidance systems tested. BACKGROUND TO THE STUDY There has been little published research on how emergency lighting, escape route lighting and wayguidance provision may work in a smoke filled building. Earlier studies include those by Webber and Aizlewood 1, Jensen 2, Paulsen 3, Heskestad and Pedersen 4 and Heskestad 5. The aim of the present research is to compare human behaviour with different escape route lighting and wayguidance systems in smoke logged conditions in order to contribute to the development of appropriate standards. Current recommendations for escape route lighting, contained in British Standard BS 5266 Part 1 6, require the provision of a minimum of 0.2 lux on the floor on the centre line of the escape route. The recommendations in BS5266 Part 1 are based on research which involved measuring the performance achieved by fully sighted people in clear air. It cannot be assumed that the same lighting will provide acceptable conditions for people in a smoky environment. Whilst BS 5266 Part 1 is concerned with the application of conventional emergency lighting luminaires, there are now a variety of alternative forms of emergency and escape route provision including, for example, low mounted light emitting strips, generally called wayguidance systems. This different approach is covered in BS 5266 Part 2 7 for electrical low mounted way guidance systems. Their aim is to provide a good contrast that indicates the escape route, rather than illuminate the whole of the building space along the route, and let the fabric of the building give the contrast that people need when seeing where to go. EXPERIMENTAL CONDITIONS AND PROCEDURE How was the performance of the lighting systems examined? This paper looks at four kinds of wayguidance provision, and compares them firstly with the British Standard (BS 5266 Part 1) emergency lighting system, and secondly with normal

2 overhead lighting. It was decided to include normal lighting as a test system because it is possible that people may have to evacuate a smoke filled building with the conventional lighting left on. The systems were tested by having eighteen volunteers pass through a purpose built two storey office layout under the different lighting conditions. The main objective measure was people s walking speed along different parts of the route. The escape route that people walked through started in an office, went though a door onto a short landing, turning down a flight of stairs, and along two sections of a corridor (a short one, 6 metres long, in the stairwell leading onto a long one, 13 metres in length), to an emergency exit door. The route is about twenty-nine metres long. This facility is based at the Building Research Establishment, and has been used to carry out testing in clear air in earlier studies of performance of normal sighted subjects by Aizlewood and Webber 8 and Wright et al. 9. The subjects speeds were calculated from video recordings taken with one low-light-sensitive camera, and three thermal imaging cameras. The procedure that was followed was to start everyone in the office under normal lighting conditions, approximately 400 lux. The volunteers were read the following statement. We have a range of emergency lighting systems that we would like you to give us your opinion on. We will put smoke along a route and then ask you to walk through the route, using the lighting provided. Go to a mock exit door at the end of the route, touch it, then return along the same route. You will be able to tell that you have got to the correct door because there is a horizontal bar mounted on it. There are 3 ways we are going to test how good the lighting is in the smoke, the first way is to see how long it takes you to get to and from the exit door, so we would like you to walk as quickly as you feel it is safe for you do to so in the smoke, do not run, and go at your own pace. The second way we are testing it is by asking your opinions about the lighting, and I will do that after you are back in the office. The third way we are testing it is by trying to see how far away you can see the signs on the exit door. To do this I will give you a beanbag to drop when you think you can see the exit signs on the door. It does not matter if you do not get this exactly right, do not go back and try to move the bean bag once you have dropped it, and do not slow down from what you think is your safe walking speed to try and drop it exactly. I will take you to the exit door of this office, and the smoke filled route starts on the other side. The route involves a short landing, a flight of stairs going down, and a long corridor to the exit door. The important thing to remember is that if you want to stop the test at any time then just let us know, and we will come and collect you and bring you back here. After they had been sitting under the normal lighting for ten minutes, to allow their eyes to adapt, the main lights were switched off and they set off along the route under one of the lighting conditions. After they had completed the route (out and return) they were asked a series of questions under 400 lux. This procedure was repeated until all systems had been seen. Different volunteers went through the test route in a different order of lighting conditions, determined by a Latin square system, to try and eliminate any effects from learning the route. After all six lighting systems had been seen the first one was repeated, to allow comparisons to be made concerning learning the route. Before the walk-through tests the subjects carried out two simple visual tests: a visual acuity tests; the other test was a measure of visual field. All eighteen subjects had good corrected vision. The age of the 18 subjects ranged from 23 to 63 years, with a mean age of 46 years. There were 7 men and 11 women.

3 What lighting systems were examined? Six lighting systems were studied, covering a range of illuminances and approaches to wayguidance systems. The photometric details in the following sections all refer to data collected in clear air. Overhead emergency lighting. This follows British Standard 5266 Part 1, which recommends a minimum of 0.2 lux of illuminance on the floor along the centre line of an emergency escape route. This compares with other European countries value of a minimum of 1 lux on the floor 10. In fact the illuminance provided by the system along the escape route was greater than the minimum recommendation of the British Standard, having a minimum value of 0.68 lux, see Table 1. The light was provided by six 4 Watt fluorescent luminaires mounted above head height. There was a fluorescent sign (164 mm in height, 394 mm wide) mounted at a height (to base) of about 1.7 metres on the exit door. The format of the graphical symbols of the safety sign were to the EU Directive 11. The only signage along the route was at the turn from the short corridor into the longer corridor, where an externally illuminated sign was placed at a height of approximately 1.7 metres. The green area of this sign was 149 mm in height, by 210 mm wide. The format of the graphical symbols were to the EU Directive. There was about 6 lux incident on this sign. Normal lighting. In the corridor this system consisted of six fluorescent luminaires mounted on the ceiling. In the stairwell there were two ceiling mounted incandescent luminaires. The area before entering the escape route was not lit but photoluminescent lines and door marking helped the subject find the entrance door; once within the escape route the minimum illuminance was 19.6 lux. Again there was a fluorescent sign (164 mm in height, 394 mm wide) mounted at a height of about 1.7 metres on the exit door. The format of the graphical symbols of the safety sign were to BS 5499 Part 1 12 and ISO The only signage along the route was at the turn from the short corridor into the longer corridor, where an externally illuminated sign was placed at a height of approximately 1.7 metres. The green area of this sign was 130 mm in height, by 430 mm wide. The format of the graphical symbols of the safety sign were to BS 5499 Part There was over 80 lux incident on this sign. Electroluminescent wayguidance system. This consisted of a green electroluminescent track mounted on the wall at 1000 mm above the floor. On the escape route, the track ran continuously along the right side (outward journey) of the route and along the pitchline of the stair. A track was also mounted on the left side of the narrow section of the corridor. The width of the track was 24 mm. Mounted on the track were projecting clear plastic wedges spaced about 260 mm apart, provided as a directional aid through touch. The final exit door was marked by a vertical strip on the right side, bottom 900 mm from floor, top 1900 mm from floor. In the office, prior to the start of the escape route the track was mounted on the wall at a height of 1000 mm together with a white electroluminescent notice with text and figures giving advice on how to use the touch features

4 of the track. The luminance of the track ranged from 18 to 26 cd/m 2. The track met the luminance recommendations of BS5266 Part 2 in terms of luminance and width. The minimum illuminance along the route was 0.25 lux, which meets the illuminance recommendations of BS 5266, which calls for a minimum of 0.2 lux on the centre line of the escape path. There were two internally illuminated signs with this system, one on the mock exit door at a height of approximately 1.5 metres, with a green background area of 150 mm in height and 210 mm wide. The other sign was at the turn into the long corridor, and placed at a height of approximately 1.5 metres. The green area of this sign was 149 mm in height, by 210 mm wide. The graphical formats of both signs were to the EU Directive. LED wayguidance system 1. This system had wall mounted tracks along the escape route. These were fixed at between 200 and 240 mm above the floor. In the stairwell the tracks were on both sides, and on the stair the tracks followed the pitchline 160 mm above the nosings. In the corridor, the track was on the right side only (in outward direction). Only the mock exit door along the escape route was outlined, and the right hand side track continued across the side doors. The area before entering the escape route had a track on the wall and the door leaving the office was outlined. The tracks had green 35 mcd illuminator LEDs every 25 mm pointing downwards and inwards to the floor of the escape path, and green 35 mcd marker LEDs every 100 mm pointing upwards and inwards towards the eyeline of an escapee. There were six 15 mcd LEDs mounted in each of the stair nosings. The door frame markers consisted of 35 mcd LEDs spaced 50 mm apart. The minimum illuminance along the route was 0.25 lux, which meets the recommendations of BS 5266 and the track meets the intensity and spacing recommendations of BS 5266 Part 2. The signage for this system was entirely pictorial, with a pictogram on the mock exit door at approximately 1.4 metres, (size 80 mm high, format to EU Directive). There were seventeen 50 mm high arrows made up of thirteen LEDs indicating the way to the exit, mounted between 800 and 900 mm high. LED wayguidance system 2. This consisted of a floor mounted track in the long corridor combined with the LED system 1, described above, in the stairwell, stair (except that the stair nosing LEDs were not switched on), landing and start area. The floor track was along the full length of the left side of the corridor (on outward journey) and continued to the mock exit door and joined up with a vertical strip marking one edge of the door up to door handle height, 1230 mm. The track consisted of LED triplets grouped together with spacing between triplets of 200 mm. The mean peak intensity of the green LEDs was 140 mcd. The track meets the intensity and spacing recommendations of BS 5266 Part 2. However, the minimum illuminance along the route was 0.16 lux, which does not meet the recommendations of BS This is because along the long corridor the light was produced by the wall mounted arrows and the floor mounted track. The floor mounted track produced light upwards to give information to the eye, but does not directly illuminate the floor. The mock exit door sign was an LED sign with the vertical text EXIT. Height 580 mm to base of sign. The sign had a white painted base and the LEDs were recessed behind a translucent cover. The letter height was 48 mm, stroke width 7 mm. The mean peak intensity of the LEDs was 117 mcd. The other directional information along the escape route was provided by seventeen arrows 50 mm high arrows made up of thirteen LEDs indicating the way to the exit, mounted between 800 and 900 mm high.

5 Miniature incandescent wayguidance system. This system had light produced by very small incandescent lamps, giving a whitish light. The light strip with lamps of mean intensity 100 mcd and 100 mm apart met the intensity and spacing recommendations of BS 5266 Part 2. The strips were mounted about 180 mm above the floor, apart from in the stairwell where they were mounted on the floor. Because the strips were mounted in the floor the minimum illuminance in this section of the route was less than that called for by BS The tracks went down both sides of the corridors and stair, and outlined the doorways on the escape route. The minimum illuminance along the route was 0.15 lux. There was a fluorescent sign (164 mm in height, 394 mm wide) mounted at a height of about 1.7 metres on the exit door. The format of the graphical symbols of the safety sign were to BS 5499 Part 1 12 and ISO There were no internally illuminated signs indicating the way to go to get to the exit door. However there was only one decision point along the route, deciding whether to turn left or right at a T-junction. Turning left revealed a 1.5 metre length of corridor with a dead end. Turning right showed the thirteen metre corridor leading to the exit door. At this point there was an externally illuminated sign placed at a height of approximately 1.7 metres. The green area of this sign was 130 mm in height, by 430 mm wide. The format of the graphical symbols of the safety sign were to BS 5499 Part There was less than 1 lux incident on this sign. Table 1: Mean (and minimum) horizontal illuminance (lx) measured on centre line of escape route. Office Landing Stair Stairwell Corridor Emergency 1.94 (1.88) 1.81 (1.44) 1.06 (0.89) 0.99 (0.77) 1.96 (0.68) Normal 0 (0) 57.8 (35.3) 47.5 (30.0) 37.4 (19.6) 165 (116) Electroluminescent 0.62 (0.47) 0.50 (0.34) 0.54 (0.44) 0.62 (0.33) 0.51 (0.25) LED system (1.65) 5.61 (3.00) 4.28 (3.43) 4.31 (2.16) 0.70 (0.33) LED system (1.65) 5.61 (3.00) 4.28 (3.43) 4.31 (2.16) 0.38 (0.16) Incandescent 1.86 (1.48) 1.69 (1.21) 1.21 (0.69) 0.22 (0.15) 1.80 (0.58) Smoke generation The simulated smoke was generated from a mineral based fluid and was white and non-toxic. The escape route was filled with smoke from two smoke generators, one at the mock exit door, the other within the stairwell. The air/smoke mixture was well mixed before the subjects entered the route. The smoke density was measured at seven positions on the route, four positions in the long corridor, and three in the stairwell at three different heights. The smoke density meters were based on IR light sources so that they did not present any visible light and visual cues to the subject. Data from the smoke meters was continuously logged on a computer and timing was synchronised with the video recordings. This enabled smoke density values corresponding to the location of the subject at the time to be determined. A HSE report 15 on testing the performance of low mounted wayguidance systems in smoke proposed that the optical density of smoke should be at least 0.5 m -1 or at a higher criterion of at least 1.5m -1. From pilot tests it was found that optical densities between 0.5 to 1.5 m -1 could be produced on the escape route and that piloted subjects could traverse the route in these smoke densities. Although it was attempted to produce a standardised smoke condition for all subjects, there was some variation between runs. The mean smoke density

6 for the long corridor was 1.1 m -1 and for the stairwell was 1.2 m -1. There was no statistically significant difference between the smoke densities for the different lighting conditions. RESULTS The time taken for the subjects to walk through various sections of the route was taken from video recordings made from the cameras. The route was split into four sections: the landing; the stair; the short corridor in the stairwell; the long corridor from the turn out of the stairwell to the exit door. The level sections of the ground floor were split in two because of the large differences in the illuminances in these two parts of the route for some lighting systems (see Table 1). The statistical analysis carried out on the data was a parametric ANOVA test, to see if there were any significant differences between the walking speeds achieved under the six different lighting conditions. If there was a difference at a significance level of p<0.05, then independent samples t-tests were carried out between data sets of walking speeds under two lighting systems. Again significance levels of p<0.05 are reported. The walking speeds for the outward part of the journey are reported here. The data are from all seven runs. Landing Crossing the landing included the search for the top step of the stair. Any uncertainty in locating the first step would be indicated here. The mean walking speeds plotted against the mean illuminance in this section of the route are presented in Figure 1. The error bars show the standard error associated with each walking speed. Mean Walking Speed (m/s) LED 2 LED 1 Incandescent Electroluminescent Normal Overhead Emergency Mean Illuminance (lux) Figure 1 The mean walking speeds crossing the landing for the six lighting conditions. The two overhead lighting systems caused people to walk significantly more slowly than three of the wayguidance systems, both LED systems and the miniature incandescent wayguidance system. In addition both LED wayguidance systems allowed people to walk significantly quicker than the electroluminescent wayguidance system.

7 Stairs Going down the stair both overhead lighting systems, normal and emergency, caused people to walk more slowly than when using either LED wayguidance system 1 or the electroluminescent wayguidance system. The data are presented in Figure 2. Mean Walking Speed (m/s) LED 2 LED 1 Incandescent Electroluminescent Normal Overhead Emergency Mean Illuminance (lux) Figure 2 The mean walking speeds descending the stair for the six lighting conditions. Stairwell In the stairwell the overhead emergency lighting again caused people to walk significantly more slowly than three of the wayguidance systems, both LED systems and the electroluminescent wayguidance system. In addition both LED wayguidance systems allowed people to walk significantly more quickly than when they used normal lighting. It is seen that a system that produces almost ten times as much illuminance on the floor from overhead lights actually causes people to walk more slowly than one which produces light from low mounted strips. See Figure 3. Mean Walking Speed (m/s) LED 1 LED 2 Incandescent Electroluminescent Normal Overhead Emergency Mean Illuminance (lux) Figure 3 The mean walking speeds through the stairwell for the six lighting conditions.

8 Long Corridor In the long corridor the overhead emergency lighting causes people to walk significantly slower than the four wayguidance systems. The slowest of the wayguidance systems gives a mean walking speed along this straight level corridor of 0.75 ms -1, compared to 0.53 ms -1 for the overhead emergency lighting. Normal overhead lighting also caused people to walk significantly more slowly than when using either of the LED wayguidance systems or the miniature incandescent system. It is to be noted that LED wayguidance system 2, which does not meet BS 5266 in this section of the route, allows people to walk more quickly than overhead emergency lighting which does meet BS 5266, in fact it exceeds it by a factor of over three. See Figure 4. Mean Walking Speed (m/s) LED 2 LED 1 Incandescent Electroluminescent Normal Overhead Emergency Mean Illuminance (lux) Figure 4 The mean walking speeds along the corridor for the six lighting conditions. CONCLUSIONS From the results from eighteen fully sighted people presented here, it is clear that statistically significant differences occur between the six lighting systems tested in this paper. The lighting systems were tested in fairly uniform smoke densities of around 1.1 m -1 for a long corridor, and around 1.2 m -1 for a stairwell. The smoke was white and non-toxic. These results show four main points. 1. On all parts of the route the traditional overhead emergency lighting which meets, and exceeds BS 5266 Part 1, by at least a factor of three, causes people to walk significantly more slowly than some of the wayguidance systems tested here. In some cases this system is slower than all wayguidance systems tested, even those that do not meet the all requirements of BS 5266 Part 2 on all parts of the route. 2. Simply increasing the illuminance of an overhead lighting system does not radically increase the speed that people are prepared to walk at. Even under normal lighting conditions, with a minimum of around 20 lux on the floor in clear air (compared to less than 1 lux for the emergency lighting system) people still walk significantly

9 slower than when using dimmer wayguidance systems. This is shown most starkly in the long straight level corridor, where the normal overhead lighting produces at least 116 lux on the floor in clear air, compared to three wayguidance systems which produce minima of less than 1 lux, yet allow people to walk more quickly. 3. There are no significant differences between the two LED wayguidance systems in the long corridor. This is interesting because one of them has the strip wall mounted about 220 mm from the floor, and the other has the strip on the floor. This leads to the floor having a minimum illuminance of 0.16 lux for the floor mounted track, and about twice that for the wall mounted track, yet the walking speeds achieved by the subjects are very similar. One contributory factor may have been the fact that both systems had the same provision of directional arrows in the long corridor. 4. The effectiveness of wayguidance systems is not just a factor of the illuminance produced on the floor as analysed here but also importantly in terms of the direction of the viewing of their light sources providing visual cues which outline the escape route and emergency exit doors. Here factors affecting their effectiveness will include the photometrics of the light track, its orientation and location. ACKNOWLEDGEMENTS This research project was funded by the EPSRC. REFERENCES 1 Webber, G.M.B., and Aizlewood, C.E. (1993). Investigation of Emergency Wayfinding Lighting Systems. Proceedings of the LUX Europa 1993 Conference, Edinburgh, April 1993, pp Jensen, G. (1993). Evacuating in smoke: Full scale tests on emergency egress information systems and human behaviour in smoky conditions. IGP AS, Trondheim, Norway. 3 Paulsen, T. (1994). The effect of escape route information on mobility and way finding under smoke logged conditions. Proceedings of the Fourth International Symposium, International Association for Fire Safety Science. Ottawa, 1994, pp Heskestad, A.W., and Pedersen, K.S. (1998). Escape through smoke: Assessment of human behaviour and performance of wayguidance systems. Proceedings of the First International Symposium on Human Behaviour in Fire, Belfast, 31 August- 2 September 1998, pp Heskestad, A.W. (1999). Performance in Smoke of Wayguidance Systems. Fire and Materials 23 (6), BS 5266 Part 1 (1999). Emergency lighting. BSI, London. 7 BS 5266 Part 2 (1998). Code of practice for electrical low mounted way guidance systems for emergency use. BSI, London. 8 Aizlewood, C.E., and Webber, G.M.B. (1995) Escape route lighting: Comparison of human performance with traditional and wayfinding systems. Lighting Res. Technol. 27 (3) pp Wright, M.S., Cook, G.K., and Webber, G.M.B. (1998). Some emergency lighting and way guidance systems and the normally sighted: an experimental study. CIBSE National Lighting Conference, Lancaster, 5-8 April 1998, pp BS EN 1838 BS 5266 Part 7 (1999). Lighting applications Emergency lighting. BSI, London.

10 11 European Council Directive, 1992, 92/58/EEC. Minimum requirements for the provision of safety signs at work. 12 BS 5499 Part 1 (1990). Specification for fire safety signs. 13 ISO (1987). Fire Protection Safety signs. 14 BS 5499 Part 4 (2000). Safety signs, including fire safety signs Part 4 Code of practice for escape route signing. BSI, London. 15 HSE Offshore Technology Report OTH533 (1998). Emergency Way Guidance Lighting Systems Phase 1. Prepared by Building Research Establishment Ltd for the Health and Safety Executive (BRE authors G.M.B Webber and M.P Shipp).