The paper presents results of experimental investigations of different phlegmatizator substances and its binary compounds used for full hydrogen combustion suppression. The work was performed in experimental facilities of three different scales (small, medium and large) at normal initial pressure and temperature range 20-120 . Ten individual substances and six binary compounds were tested in a small scale experiments. Three individual halogen containing substances capable of full suppression of hydrogen combustion were found in a series of small scale experiments (tube length 1m, ID 66 mm). The minimum concentration of the most effective substance was 11%2at 20 and 14%2at 120 in a small scale experiments. Medium scale confined and large scale unconfined experiments confirmed the possibility of full combustion suppression. The minimum concentration of the most effective binary mixture was found to be 12%2at 20 in a large scale experiments.