A gas pressure reducer comprising: - a body, - a gas intake and outlet opening into this body, - a flexible diaphragm defining with said body a regulation chamber of variable volume, - an actuation finger secured to said diaphragm, - a gas intake flow rate regulation lever cooperating with said finger, and pivotally mounted in said chamber between: - a first closure position corresponding to a maximum volume of said chamber, in which this lever seals said gas intake, - a maximum opening position corresponding to an intermediate volume of said chamber, in which this lever clears a maximum passage through said gas intake, and - a second closure position corresponding to a minimum volume of said chamber, in which this lever seals said gas intake, this lever comprising a first portion pivotally mounted on said body about a first axis, and adapted to seal said gas intake, and a second portion pivotally mounted on said first portion about a second axis and cooperating with said finger, - elastic means for biasing said diaphragm towards said position defining a minimum volume of said chamber, - a stop secured to said body, disposed between said finger and said second axis, - said finger and said stop holding said second lever portion in a position inclined with respect to said first lever portion when this lever is in said second closure position, which inclination holds said first lever portion in the sealing position of said gas intake, wherein a spiral spring is interposed between the first and second portions of the lever. - a body, - a gas intake and outlet opening into this body, - a flexible diaphragm defining with said body a regulation chamber of variable volume, - an actuation finger secured to said diaphragm, - a gas intake flow rate regulation lever cooperating with said finger, and pivotally mounted in said chamber between: - a first closure position corresponding to a maximum volume of said chamber, in which this lever seals said gas intake, - a maximum opening position corresponding to an intermediate volume of said chamber, in which this lever clears a maximum passage through said gas intake, and - a second closure position corresponding to a minimum volume of said chamber, in which this lever seals said gas intake, this lever comprising a first portion pivotally mounted on said body about a first axis, and adapted to seal said gas intake, and a second portion pivotally mounted on said first portion about a second axis and cooperating with said finger, - a first closure position corresponding to a maximum volume of said chamber, in which this lever seals said gas intake, - a maximum opening position corresponding to an intermediate volume of said chamber, in which this lever clears a maximum passage through said gas intake, and - a second closure position corresponding to a minimum volume of said chamber, in which this lever seals said gas intake, - elastic means for biasing said diaphragm towards said position defining a minimum volume of said chamber, - a stop secured to said body, disposed between said finger and said second axis, - said finger and said stop holding said second lever portion in a position inclined with respect to said first lever portion when this lever is in said second closure position, which inclination holds said first lever portion in the sealing position of said gas intake, wherein a spiral spring is interposed between the first and second portions of the lever.