Visibility of exit signs and low-location lighting in smoky conditions

The International Maritime Organization (IMO) requires that in addition to the emergency lighting all passenger ships in international traffic should have low-location lighting at all points of the escape route. IMO gives guidelines for the evaluation, testing and application of low-location lighting. To support the guidelines, the International Organization for Standardization (ISO) is preparing a standard for approval, installation and maintenance of low-location lighting systems. There are, however, no international standards for testing the performance of the lighting system. In all corridors for example, the low-location lighting system is required to provide visible delineation along the escape routes. For verifying the visible delineation of semicontinuous systems, national standards are not even available. In the present project a method of defining the maximum acceptable distance between any two light sources is presented along with several measurements of the visibility of a few light sources at different viewing angles, distances and smoke densities. The method can be applied to verify the visible delineation of semicontinuous systems.