Forward and back scattering loss compensated smoke detector

A forward scattering loss compensated smoke sensor or smoke detector and a back scattering loss compensated smoke detector are disclosed. Both systems include first and second light sources for supplying a light signal into a fluid containing particulates. Both systems also include first and second photodetector devices for detecting directly transmitted, forward scattered and/or back scattered light. A ratiometric value or signal is produced in accordance with direct versus scattered detected light levels. The selection of forward versus back scattering particulate detection devices and methods is driven by the efficiency of the scattering which is a function of light source frequencies and particulate size.