A small probe utilizing the attenuation of the beta emissions from promethium‐147 has been constructed and calibrated for measuring the suspension concentration of dusts in the range of 0.1 to 2.0 kg/m3. The absorption of beta particles (negatively charged electrons) is related to the amount of matter through which the particles pass. The probe discussed here measures the beta absorption through a 3.8‐cm path length at sample rates up to 20 samples per second. The small size of the probe (16 cm overall) allows real‐timeinsitulocal measurements of the suspension of a dust. The basic theory of operation and details of the probe operation are presented. Data from the probe for use in dust flammability experiments are also presented.