The rate of pressure rise (K-St) of explosion reactions in dust/air mixtures under atmospheric conditions is an important safety parameter for describing the kinetics of explosions. The value is used during the planning of protective measures like pressure release or suppression systems. The K-St is not a value inherent to the substance, since it varies according to the shape of the test apparatus, ignition energy, time delay, and dispersion system, which all affects the degree of turbulence. Keeping these boundary conditions constant the K-St is determined essentially by the chemical properties of the dust and its reactive surface area. 3-4 fractions differing in particle size distribution between 7 pm and 400 gm and in related specific surface area were produced from four carbonaceous dusts (activated charcoal, polyethylene, lignite and sucrose), and the K-St values of the fractions were determined by experimentation. The experimental results were classified into four stages depending upon the suitable surface concentrations and the different processes involved. The stage in which dp/dt changes in surface concentration are most intense comply best with the Arrhenius equation. As a function of the specific geometric surface area, the K-St value characterizes the chemical reactivity of the substance clearly and permits extrapolation to other particle size distributions. (C) 2017 Elsevier Ltd. All rights reserved.