The invention relates to a gas regulating valve (1) for a respiratory system comprising: &mdasha main path between an inlet (2) and an outlet (3), and &mdashan evacuation path between the outlet (3) and an evacuation orifice (4), characterized in that: &mdashthe main path is provided with at least a non-return valve for preventing gas to circulate from the outlet (3) to the inlet (2), and &mdashthe evacuation path is provided with an obstructing membrane (10) arranged and designed for being deformed by gas from the inlet (2) to partially or fully obstruct the evacuation path. The invention also relates to a mask integrating such gas regulating valve, and to a respiratory system also comprising such gas regulating valve.
