Optical Density of Smoke (OD) 1 : Smoke obscuration described in terms of logarithmic ratio of initial light intensity to instantaneous light intensity
NFPA 262 Standard Method of Test for Flame Travel and Smoke of Wires and Cables for Use in Air-Handling Spaces, 2002 ed. https://www.bicsi.org/pdf/presentations/winter_11/ Telecommunications%20Cable%20-%20Steven%20Galan.pd f, (Std: Meth of Test for Flame Travel and Smoke of Wires and Cables for Use in Air-Hndlg Spaces - Amer) {278 NFC}