3. Assessment of smoke quantity

3.1 Principle

All visibility assessment models are based on smoke opacity, expressed as concentration, extinction coefficient or optical density. Opacity is therefore the experimental parameter for determining visibility. Smoke opacity can be assessed by two main families of methods.

The main characteristics of soot in fumes are overall mass concentration, and by size, particle size distribution, chemical composition and morphology. This article focuses on the overall optical effect generated by soot and other components in fumes, rather than on the detailed measurement of the particles making up the fumes. For this, please refer to ISO 29904 or to [R 2 360] .