Running Men and Cat's Eyes

Would it be better in the case of smoke filled areas to extinguish all normal and emergency lighting and rely upon powered way guidance?

Dave Hoyle,
Managing director of Hoyles Electronic Developments Ltd
www.hoyles.com
First reproduced in Fire Safety Engineering (FSE) Magazine
April 2002

The idea of illuminating, signing and marking the safe escape routes from buildings is not of course new. The principles are set in legislation and building codes the world over. No one would deny that some form of way guidance or marking is essential to the safety of people in buildings, particularly large buildings that are unfamiliar to them.

During recent years there have been many advances in escape route markings within buildings. Certainly within Europe all signage follows a familiar pattern. The Health and Safety (Safety Signs and Signals) Regulations became law in the UK on 1st April 1996. The Regulations implement the European Safety Signs Directive (92/58/EEC) which has been designed to standardise Safety Signage across Europe and ensure that with the free movement of labour, there is no risk of safety signs being misunderstood. Perhaps the most used sign is the running man displayed as white on green and often accompanied by some country specific wording. This process has been ongoing now for the last fifteen years or so and it is rare to see non-compliant signage. The exception being in American built aircraft where red on white still prevails. The most obvious improvement on the humble screen printed sign is the use of photoluminescent material. Recent advances in this technology means that this type of signage and way marking is snapping at the heels of conventional emergency lighting and electrically illuminated exit signs.

Photoluminescent materials and electrically powered systems both give similar performance in terms of duration and life expectancy. In the case of the former this can be measured in hours for both systems and for the latter it is measured in years for electrically powered systems and perhaps decades for photluminescent, notwithstanding damage. Perhaps the trigger for the growth of photoluminescent systems has been its low cost compared to electrical systems. Low cost in terms of both materials and the installation cost. Retro-fitted electrical systems also create a certain amount of disruption if the building remains in use. Regular maintenance is also a bigger issue for electrical systems.

The simplest form of way marking, and the one that is used most often in small buildings, is of course the straightforward EXIT sign with a running man and a directional arrow. This is often sufficient for a small single storey building such as an office or small factory, particularly where sleeping accommodation is not provided.

In buildings where a loss of electrical power would lead to escape routes being left in darkness then photoluminescent signage is often used. This can give useful indication for a sufficiently long period to contribute to the safe egress from a building. This type of signage often needs to be supplemented by emergency lighting to help escapees to find their way more easily. It is also essential that photoluminescent signage is used in normally well lit areas in order that saturation excitation can be acheived. Whilst a glow is still evident when excited in poorly lit conditions it will generally have a lower starting luminance and therefore arrive at its end point luminance earlier. In this respect it is doudtful that photoluminescent signage will ever compete with the performance of electrically back lit signs.

In large buildings such as hospitals and colleges where escape routes may be long and sometimes complex, a stranger can easily become disoriented in low light levels. In the case of hotels when residents may have just awoken the problem is much more acute. Photoluminescent marking strips can be used to good effect in these situations, however, costs do start to rise if the job is to be done properly. The inherent yellowish colour of photoluminescent material is not always compatible with the existing or proposed decor in a building. This is particularly true in listed buildings.

The greatest danger of course is a combination of loss of electrical power and fire. In such a situation time is of the essence. In the early stages the rapid spread of smoke is the problem. In general smoke will rise to a ceiling. It is only a matter of seconds before conventional signage situated at or above head height becomes obscured. Seconds later photoluminescent signs are obscured. Electrically powered back lit signage will continue to be useful for some minutes. However, even these can become totally obscured beyond about 5 metres within five to ten minutes.

In recent years low mounted electrical way guidance systems have been developed. The floor mounted strip lights are very familiar to airline passengers and have in fact become standard on many passenger aircraft. Similar systems are available for shipping and for installation in buildings, often as wall mounted systems.

BS5266: Part 2:19981 is a code of practice for such systems. The low mounted way guidance systems as envisaged in this standard are designed to illuminate when smoke is detected. They must therefore integrate with a smoke detection system in the building. They are designed to supplement emergency escape route lighting not to substitute it. In order to comply with Part 2 of the standard many of the component parts and certain performance criteria must also comply with Part 1, eg power supplies and duration. A system complying with these standards presents a virtually continuous line of luminous white or green tracks. The light sources are often light emitting diodes (LEDs) or electroluminescent elements2. These systems are excellent for new buildings but their widespread use is still somewhat limited due to the relatively high component cost, typically £35 per metre, and the high cost of installing the track, associated wiring and power supplies etc. Regular maintenance is also essential if only to verify functionality.

Necessity is the mother of invention and it is often the necessity to reduce costs that inspires us to look at new solutions. Most fire prevention officers, for example, will confirm that the single biggest saver of lives in domestic fires has been the relatively inexpensive battery powered residential smoke detector. Twenty years or more ago such detectors were relatively expensive though considerably cheaper to buy and install than conventional detectors used on systems. Had the residential smoke detector never been invented it is extremely unlikely that conventional detectors would have penetrated the residential market and the contribution they have made to saving lives would have been lost. Many industry professionals at the time regarded the residential smoke detector as a toy, insisting on FOC approval or nothing.

In developing their way guidance system HOYLES ELECTRONIC DEVELOPMENTS sought to develop a more economical system of way guidance markers. The system is similar to reflective road markings, however, high brightness LEDs are used instead of cat's eyes.

To be economical the material cost had to be less than the conventional way guidance strip systems and of course installation costs had to be massively reduced. In order to achieve this it was necessary to compromise the accepted standard.

The HOYLES way guidance system, EXITi, is a completely self contained battery powered LED system. No central power supply is required nor is it necessary to integrate it with any fire or smoke detection system or install any wiring. The LEDs are ultra bright high efficiency types that require only about 5% of the power of conventional LEDs. As there is no external control to each unit the LEDs are permanently active but flashed to conserve battery power. An estimated battery life of 5 to 6 years can be achieved by the EXITi. Two LEDs are provided, one green and one red in each unit. Following the green LEDs leads an escapee out of the building. The red LED is included to assist the fire brigade in searching a smoke filled building in the reverse direction. The intensity, flash rate and mark space ratios are chosen to give penetration of smoke at up to five metres. The green LED gives one flash every 1.5 seconds and the red LED one flash every 4.5 seconds. The two part IP65 clear polycarbonate enclosure houses the control circuitry, batteries and LEDs and has a lens at each end to focus the light into a directional cone.

Tests were conducted in the Merseyside Fire Brigade3 Test House to determine the light penetration of the green LEDs at increasing smoke densities. It was found that the latest technology green LEDs are able to penetrate dense smoke at what the fire brigade considered to be un-survivable levels without breathing apparatus. Comparisons were made against a mains powered back illuminated exit sign with downlighter. At the point where the exit sign and downlighter became totally obscured and ineffective a high efficiency green LED mounted 400mm from floor level was still able to give penetration for guidance purposes at five metres.

Research at the Department of Construction Management & Engineering of Reading University4 into the effects of smoke on walking speed for normally sighted people using overhead lighting and wayguidance provisions concluded that traditional overhead emergency lighting causes people to walk significantly more slowly than some of the way guidance systems tested. Even under normal lighting conditions people still walk significantly slower than when using the dimmer wayguidance systems. The wayguidance sytems used were of the LED, electroluminescent and incandescent types in the form of wall or floor mounted tracks.

Similar results5 were obtained in different tests using visually impaired people. On a scale of 1 to 7 (1 very easy and 7 very difficult) LED way guidance scored in the range 2 to 3 whereas photoluminescent strips and tapes increased the degree of difficulty to over 6.

The results from Reading almost beg the question; is it better in the case of smoke filled areas to extinguish all normal and emergency lighting and rely upon powered way guidance.? Imagine driving a car through fog with street lights but no cat's eyes.

It is perhaps unfair to compare the HOYLES EXITi system against low mounted luminous track systems in terms of performance. However, due to its low component and installation cost the company believes its new way guidance product will be specified in a growing number of buildings where luminous track and photoluminescent systems will prove to be too expensive. The EXITi is marketed with a multilingual (English, French, German and Italian) Fire Action notice.

REFERENCES and ACKNOWLEDGEMENTS

1. BS5266: Part 2:1998 Code of practice for electrical low mounted way guidance systems for emergency use.

2. Lyteline Technology Ltd.

3. Merseyside Fire Brigade for their assistance and use of the fire test house.

4.http://www.rdg.ac.uk/AcaDepts/kc/nhe/research.html download bstnspeedfin.pdf

5.http://www.rdg.ac.uk/~keswrims/nlc96.html