The burning velocity and the nature of the H2/F2flame at various gas compositions gas compositions have been experimentally determined. It was found that reactions induced by a diffusion-type flame proceed rather slowly, but reactions triggered by a compression wave proceed with supersonic speed. Based on the measurements of gas stability, repetetive pulse operation of H2/F2chemical lasers at atmospheric pressure has been achieved. The second and third explosion limits of H2+ F2reactions in O2/He mixtures were also studied experimentally to improve our understanding of the nature of H2+ F2explosion. The apparatus allowed the simultaneous time-resolved measurement of both gas pressure and temperature at the center of the spherical reaction vessel. It was found that, for fixed H2+ F2total pressure and O2concentration, mixtures with higher F2/H2ratios are less stable and explode at a lower temperature. It appears quite certain that molecular O2plays an important role in the chain termination reaction. However, the addition of CF4, SF6, or N2showed no effect on the boundaries of the H2/F2explosion.