Method and device for determining of explosivity rate of gaseous medium

A method of determining the explosivity rate of a gaseous medium containing at least one explosive gas, with a detecting filament which is heated in said medium by an electric current flowing therethrough, comprising the steps of:

• igniting said detecting filament through connection thereof to a power supply,
• regulating power supplied by said power supply to said detecting filament so as to maintain constant the resistance thereof,
• taking into account, at some successive moments counted from the filament ignition time, the value U(t) of a quantity U which is significant for the power supplied to said detecting filament,
• extrapolating from said values U(t) an exponential curve of equation ##EQU6## by identifying the parameters U.sub.o,i and k.sub.i thereof, n being an integer greater or equal to unit k.sub.i being a positive real exponent expressed in sec.sup.-1, and
• introducing parameters U.sub.o,i and k.sub.i into a process function F, where the process function F is an empirically predetermined mathematical function with twice n parameters, which process function F is adapted to provide from these parameters an estimation of the initial explosivity rate of such gaseous medium independently of the nature of the explosive gas present in such gaseous medium.