Photometric measurement of visibility in case of fire

Limited visibility in case of fire is a major tenability criterion in performance-based safety concepts. The smoke density can be calculated with CFD codes, yet there are many indicators that the light extinction is overestimated. In order to improve the predictions, it is important to create a reliable experimental data basis for modeling light obscuring effects. Especially, spatially resolved data of the extinction coefficient is important to evaluate CFD-based model prediction.A new photometric measurement method for the spatial and time resolved determination of light extinction coefficients within the scope of laboratory fire experiments was recently presented. A camera captures the relative change in intensity of individual light sources (LEDs) due to the fire smoke. Based on geometrical optics and the Beer-Lambert's law, an inverse model deduces the local values of the extinction coefficient. This initial study covered only one experiment with a single LED set in a EN 54-9 test fire.This poster presents an extension of the previously described method in terms of the evaluation scope as well as the range of the experiments. In addition to the N-heptane pool fires, various solid and smoldering fires were investigated. By using multiple LED strips and a second camera, the analysis can be extended to a two-dimensional scale while local deviations of the smoke density can be recognized. This new experimental data set creates a fundamental basis for visibility model validation