To provide a gas producing valve opening device which obviates the need for an impact absorbing device by using the peak pressure of the gas produced by sodium azide as a valve releaing force, is consequently capable of regulating the pressure resistance to the pressure to be intrinsically used, is, therefore, necessitated to have lower rigidity and is made simple and inexpensive.

This gas producing valve opening device is constituted to produce the has by a gas producer using chemicals, such as sodium azide, and to open a fire extinguishing agent container valve of a fire extinguishing device, etc., by actuating a piston for valve opening with the gaseous pressure. In such a case, the max. value G in the output curve X of the piston is so set by regulating the gaseous pressure as to deviate slightly in a direction where the force is large than the value of the valve opening force D at the curve Y of the force necessary for opening and holding the dire extinguishing agent container valve on the graph having force at the axis of abscissa and time at the axis of ordinate so that the fire extinguishing agent container valve is opened just before the output of the piston is maximized.