The objective of this program was the development, design, fabrication, and laboratory testing of a mine-worthy continuous respirable dust monitoring system (crdms). The operation of the sensor unit of the system is based on the light scattering intensity of the respirable fraction of the airborne dust. The crdms is compatible with the typical environmental rigors that characterize coal mines, and, in particular, the shock, vibration, impact, moisture, and dust conditions prevailing at active mining machines. The sampled area must be within the breathing zone of the mining machine operator whose dust exposure is to be monitored. Instantaneous, as well as shift-averaged dust concentrations, are displayed and recorded for later retrieval. Alarm indications and other diagnostic information are provided.