Gives guidance on: a) optical measurement of smoke obscuration; b) general aspects of optical smoke test methods; c) consideration of test methods; d) expression of smoke test data; e) relevance of optical smoke data to hazard assessment. The main changes with respect to the previous edition are listed below: - Modified title. - Updated normative references. - Expanded terms and definitions. - Numerous editorial changes of a technical nature throughout the publication. - A flowchart has been added for the evaluation and consideration of smoke test methods. Has the status of a basic safety publication in accordance with IEC Guide 104