Candela effective is based on candela seconds and attempts to equate the brightness of a flashing light source to the brightness of a steady burning source. If a flashing light has a candela effective rating of 100 then it will be visible at the same distance as a 100 candela steady burning source. The National Bureau of Standards, the FAA, and the Illuminating Engineering Society use candela effective in specifying intensities of flashing light source because this rating is the most meaningful when it becomes necessary to predict the visible range of flashing warning lights versus steady burning light sources.