Emergency illumination must be provided in case of power failure in public buildings or places of work. A laboratory study of the mobility of subjects under simulated emergency illumination was performed to determine the level of emergency illumination necessary for a rapid exit, and to establish whether this level depends upon the normal illumination. Both young and elderly subjects were used. The experimental conditions were selected to simulate situations in which the occupants are not familiar with the escape route. In addition to measuring the time that the subjects needed to complete an escape, the subjects were asked to evaluate the lighting on several scales; and their #x2018;spare mental capacity#x2019; during the escape was measured by their performance on a secondary mental task. The results showed that all measures of performance worsen as the emergency lighting is decreased below 2 Ix. The figure of 2 lx is appropriate for both normal light levels tested, 250 and 1000 lx. Where many elderly people are apt to be present, a minimum of 41x is advisable. These recommendations are higher than those prescribed by the British Standards (0-2 lx) and the Deutsche Industrie Norm (10 lx).
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