Relevant specifications in the field of gas supply provide for different safety devices for installation in a gas-supply system, in particular, an acetylene-supply system. To provide such a safety device, which is characterized by a compact structure and a high level of operational reliability, this invention proposes that a valve body (1) incorporates an over-pressure valve (4; 104) of a quick-action shut-off device, a control valve (3; 103) of a pressure-limiting device, and a safety valve (2; 102), whereby the safety valve (2; 102) can be fluidically connected to the over-pressure valve (4; 104) and the control valve (3; 103), and closes either when the over-pressure valve (4; 104) opens due to an inlet pressure that is above the inlet-pressure limit value or when the control valve (3; 103) opens due to an outlet pressure that is above an outlet-pressure limit value.