At least two gases combine to form a detonable mixture that is detonated near an avalanche start zone. Each gas is separately supplied at a pressure above ambient pressure so that the pressure differential drives the gases through a mixer and to deploy as a detonable cloud in open air near the start zone. An igniter is located in communication with the detonable cloud near its discharge point from the mixer so that the igniter will be in communication with the cloud near the end of a predictable time interval. A controller releases the gases to initiate the mixing and deployment of the gas cloud and measures the interval. At the end of the predictable time interval, the controller fires the igniter to detonate the explosive gas mixture in open air.