CARBON DIOXIDE AS INHIBITOR FOR IGNITION AND FLAME PROPAGATION OF PROPANE-AIR MIXTURES V. Munteanu Û , D. Oancea Û and Domnina Răzuş ÛÛ The effect of CO 2 addition on stoichiometric propane-air mixtures, at ambient pressure and temperature, was analysed for both ignition and flame propagation. The quenching distance significantly increases and the normal burning velocity significantly decreases with the increase of CO 2 content. The ignition and the propagation are differentiated by their activation energies, evaluated from the flame temperature dependence of the quenching distance and the normal burning velocity, respectively. 1. Introduction An important aspect when referring to prevention of explosions in hazardous areas is the dilution effect of inert gases. If the terms in use are efficiency and cost of operation, one of the common inert gases is carbon dioxide (CO 2 ). The influence of CO 2 on several flammability parameters of stoichiometric propane-air mixture has been examined. The inert concentration in the gas phase was scanned within the range of 2%÷32%. 2. Experimental Apparatus & Procedure The quenching distance, d q , and the normal burning velocity, S u , were the two explosion parameters that have been experimentally determined. The experimental equipment contains three major parts: – gas control system that covers all gas operations and also monitors the gas flow, – explosion cell, made of stainless steel, equipped with a spark generator – two electrodes plugged into an electrical discharge circuit, and – computer-assisted data acquisition system. The explosion cell, a cylindrical vessel of 6 cm height and 6 cm diameter, made from stainless steel, was fitted with flanged electrodes for quenching distance measurements [1], and an ionisation gauge. The spacing of the electrode tips was varied with a micrometer screw and the spark gap was positioned in the centre of the vessel. The ionisation gauge was placed at a small distance, r gauge , from the spark gap, monitoring the flame propagation Û Department of Physical Chemistry, University of Bucharest, 4-12 Regina Elisabeta Blvd., 70346 Bucharest, ROMANIA ÛÛ “I.G.Murgulescu” Institute of Physical Chemistry, 202A Spl. Independentei, Bucharest, ROMANIA