Visibility analysis by light attenuation ratio recorded with portable camera at the full-scale hot smoke test site

Abstract

Some countries have enacted the full-scale hot smoke test standards to verify the effectiveness of smoke extraction systems. Unfortunately, the judgment of most performed tests is based on vision and lacks scientific value. It is important to establish a scientific and quantifiable measurement system for visibility judgment in a large space. This paper analyzed the visibility values obtained through the light attenuation in a full-scale hot smoke test site. The quadratic regression relationships between the gray scale values and the attenuation ratios were derived. The visibility of the test site can be also obtained by grayscale analysis of recorded images. A qualified emergency direction light was used as a light source, and a closed-circuit television and a portable camera were adopted for image recording. These images were converted into grayscale pictures to obtain the gray scale values at the center of the bright spot. By comparing with the light attenuation ratio of the quantifiable measurement equipment in front of the light source, the results showed excellent relevance and demonstrated the applicability of the captured images.