Emergency lighting: a survey

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Canadian Property Management, 7, 5, pp. 8-10, 1992

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Emergency lighting: a survey Ouellette, M. J.

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Emergency Lighting: A

survey

by M.J. Ouellette

ANALYZED

L I B R A R Y

Re~rinted from

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Vol. 7, No. 5, 1992

D. 8-10

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(IRC Paper No. 1810)

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Emergency Lighting: A Survey

By Michael Ouellette

A recent study of the emergency lighting in seven Ottawa office buildings suggests improvements that could be made to improve safety in large buildings.

The study showed that when main lighting failed and emergency lighting had to be relied upon, some areas, including stairwells, were totally dark. Other areas were dim enough to make evacuation slow and difficult. There we,re, however, other areas which had more than enough lighting for an emergency.

The study was done with the co- operation and assistance of Public

Works Canada. The actual

measurements were carried out by Brian W. Tansley and Associates. A technical paper describing the study has been prepared for presentation at the 1992 annual conference of the Illuminating Engineering Society of North America in San Diego in August. This is a summary of that paper.

The primary objective of the study was to determine whether the buildings surveyed would meet the emergency lighting requirements specified in

Labour Canada's Canadian

Occupational Safety and Health (COSH) regulations. Other objectives were to develop and evaluate related measurement procedures, to evaluate

existing building maintenance

practices and to comment on the

appropriateness of existing

regulations.

As it turned out, the emergency lighting in the seven buildings studied was extremely variable, especially in those with open-plan offices. There, floor layouts had sometimes been reorganized to form new aisles and exit routes but without lining up the emergency ceiling light fixtures with these new routes.

Building operations personnel

routinely tested and inspected the operation of their central emergency power systems in accordance with the National Fire Code of Canada. But it seemed less attention was paid to

ensuring that central power actually resulted in emergency lighting where it was needed.

Large sections of emergency evacuation routes were in complete darkness during the survey. Causes of darkness included failed lighting units, absence of lighting units, and, quite frequently, blockage of emergency lighting by newly erected walls and privacy panels.

One reason for this is that building operations personnel were unable to tell normal lighting fixtures and circuits from those connected to central emergency power. As a result, walls and partitions were routinely erected without regard for emergency lighting

requirements.

Where battery-powered equipment was provided, many of the units were on general-purpose circuits rather than on lighting circuits. Thus, if a lighting circuit failed, adequate emergency lighting might not be available if emergency lights were not property spaced along general- purpose circuits.

The study found it would be impossible to reliably characterize the typical emergency illumination in terms of the COSH regulations. This is

because those regulations are defined, at least in part, using arithmetic means. Over-reliance on means and averages can produce incorrect results. Consider the following analogy.

If three workers each earn $10,000 annually while another earns $170,000, then it would be misleading to say that the four of them earn $50,000 on average.

Likewise, mean illuminance in the buildings studied was strongly influenced by the relatively few brightly illuminated areas near and directly below the widely spaced luminaires. Thus our study shows that emergency lighting in six of the seven buildings was adequate because they provided mean lighting levels of 10 lux or more. In reality though, half the surveyed spaces had one lux or less of emergency lighting, and 14 per cent of the exit routes surveyed were in darkness or below the limits of sensitivity of our measuring equipment, which is 0.1 lux. That's pretty dark, and with that lighting level it would be difficult for people to find their way to safety. Indeed, that level of lighting is so low that one member of the lighting survey team fell over a potted fern while making his measurements.

A number of ideas emerged from the study. If adopted, they should improve safety in large buildings.

0

(including individual fixtures) should be tested as a matter of routine:

0 _{Building specification and}

commissioning procedures should ensure adequate emergency lighting in evacuation routes when normal lighting circuits fail. This means battery-powered units should be on lighting circuits rather than general- purpose circuits;

0 _{Emergency lighting fixtures should}

be readily distinguishable from normal lighting fixtures (e.g., by marking each emergency unit by a coloured sticker);

0 _{Operations policies should ensure}

that these fixtures receive priority for maintenance, and that floor-plan changes, such as the erection of partitions, do not defeat the effectiveness of these fixtures.

Finally, it is recommended that regulations, codes and standards on emergency lighting should not be based on means. In fact, some codes and standards around the world are already based primarily upon minimums.

This raises another question: What should that minimum be? A survey of the professional literature done for the IESNA suggests that there probably isn't any magic number, above which lighting can always be described as adequate. Indeed, it showed that there is a range of possible results needing informed design decisions. Nevertheless, the Emergency Lighting Committee of the IESNA currently favours an average of ten lux with a minimum of one lux at floor level along the centre of the escape route.

These, of course, are recommendations, and have not been included in Canadian codes, although this writer intends to propose to the committee responsible for the National Building Code that a minimum illumination at floor level be incorporated into the 1995 edition of the Code.

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technical officer with the Institute for Research in Construction, National