Visibility of Four Exit Signs and Two Exit Door Markings in Smoke as Gauged by Twenty People

This paper presents visibility distances from twenty people who have viewed six internally illuminated elements of emergency lighting systems or wayguidance systems, under different ambient lighting, in smoke. The optical density of the smoke ranges from 0.8 m to 1.4 m. The six elements investigated are four emergency exit signs with graphical symbol formats and two types of exit door markings. The distance at which the elements are first visible through the smoke are reported, under no overhead lighting, emergency overhead lighting (producing between 1 and 2 lux on the floor) and normal lighting (producing between 130 and 190 lux on the floor). Statistical analysis shows that the total optical density of the smoke between the observer and sign or door marking is not significantly different between no overhead lighting and emergency overhead lighting, however both these situations allow the element to be seen through a greater total optical density than under normal overhead lighting. Significant differences between the total optical density of the smoke that the six elements can be seen through are also reported.