This experiment involves HHO and soap bubbles that end up exploding mid-air. Oxyhydrogen or HHO gas is a mixture of hydrogen and oxygen that can combust. [WARNING: Do not try this experiment at home or without supervision.]
Using this mixture and soap to create a "bubble" of the gas, the two amateur scientists in the video create an explosion mid-air with a torch. Oxyhydrogen is combustible when it reaches about 1065 F (570 C). Once ignited, the gas releases energy and converts to water vapor with a loud, explosive noise.