The results of this study indicate that the prototype smoke detector fabricated to combine both the ionization chamber
and the optical scattering chamber functions as expected. The responses of the two components are similar to the responses previously measured as separate components. The utilization of the ratio of ionization chamber signal to optical scattering signal shows potential for use in the discrimination of very fine particles, such as those from diesel exhausts, and very coarse particles, such as mine dusts. The commercial smoke detector showed adequate response to smoldering combustion, but did not exhibit good response to flaming fires. However, the potential for the detector to be insensitive to both very small particles, such as those from diesel exhausts, because it operates on the principle of light scattering and to the larger particles as a result of the flow and filter incorporated into the detector warrant further test and evaluation under typical mine conditions.