Experimental investigations of the effect of the presence of five C 1 -halocarbons (CF 4 , CHF 3 , CF 3 I, CHF 2 Cl, and CF 3 Br) on the suppression of premixed high-speed turbulent flames and quasi detonations have been carried out in a 7.5-m long, 50-mm diameter tube. Lean and stoichiometric C 2 H 4 /air mixtures in the absence of any halocarbon, initially at 100 kPa and 295K, constitute the reference states. A primary objective of the work has been to determine the relative suppression efficiencies of different agents under highly dynamic situations, without the undue influence of either the ignition event of the mixing of the agent into the flame front. This was accomplished by generating a highly turublent flame/quasi detonation in the driver section, which contained no suppressant, followed by measurements of the velocity and pressure ratio as the wave front entered the test section of the tube, which contained suppressant premixed with the same fuel/air combination. A turublence generator in the form of a spiral obstruction was used in the tube to broaden the gas-dynamic conditions attainable by the flame. Flame and shock wave velocities up to 1300 m/s, pressure ratios across the shock fronts over 26:1, and shock wave/flame spacings of the order of 10 cm were measured with piezoelectric pressure transducers and fast photodiodes. The experimental facility was successfully employed to clearly discriminate among the dynamic characteristics of the five compounds, revealing behavior distinct from what was observed in companion studies using atmospheric nonpremixed flames. The suppression process is strongly influenced by the concentration of an agent, the structure and composition of an agent molecule, and the composition of the combustible mixture itself.