Gas dispensing unit comprising: - a main gas line comprising an inlet orifice and an outlet orifice for the gas, - a first auxiliary gas supply line fluidly connected, via a downstream end, to the main fluid line, and comprising at least one controllable valve capable of controlling the passage of gas from the auxiliary line to said main line, - a gas non-return device arranged on the main fluid line, - a first pressure sensor comprising a gas pressure port fluidly connected to the main line between the inlet and the non-return means, and/or a second pressure sensor comprising a gas pressure port fluidly connected to the main line between the non-return means and the outlet orifice, and - a control system connected to said first pressure sensor and/or second pressure sensor and controlling said at least one controllable valve in response to at least one pressure measurement taken by at least one of said sensors (12, 13), characterised in that: - the controllable valve is a solenoid valve, - the control system comprises at least one programmable controller, - at least one portion of the main fluid line, the auxiliary fluid supply line, the controllable valve, the non-return device, the first pressure sensor, the second pressure sensor and the control system are comprised in a cabinet, - and it further comprises: - a bypass line fluidically connected to the first auxiliary supply line, upstream and downstream of the controllable valve, said bypass line comprising a manual valve that can be manoeuvred by the user and that is, normally, closed, and - a case with a control panel connected to the control system, in order to display a specific alarm in order to warn the user, in case of malfunction of the solenoid valve, and allow the user to actuate and manually open the manual valve. - a main gas line comprising an inlet orifice and an outlet orifice for the gas, - a first auxiliary gas supply line fluidly connected, via a downstream end, to the main fluid line, and comprising at least one controllable valve capable of controlling the passage of gas from the auxiliary line to said main line, - a gas non-return device arranged on the main fluid line, - a first pressure sensor comprising a gas pressure port fluidly connected to the main line between the inlet and the non-return means, and/or a second pressure sensor comprising a gas pressure port fluidly connected to the main line between the non-return means and the outlet orifice, and - a control system connected to said first pressure sensor and/or second pressure sensor and controlling said at least one controllable valve in response to at least one pressure measurement taken by at least one of said sensors (12, 13), - the controllable valve is a solenoid valve, - the control system comprises at least one programmable controller, - at least one portion of the main fluid line, the auxiliary fluid supply line, the controllable valve, the non-return device, the first pressure sensor, the second pressure sensor and the control system are comprised in a cabinet, - and it further comprises: - a bypass line fluidically connected to the first auxiliary supply line, upstream and downstream of the controllable valve, said bypass line comprising a manual valve that can be manoeuvred by the user and that is, normally, closed, and - a case with a control panel connected to the control system, in order to display a specific alarm in order to warn the user, in case of malfunction of the solenoid valve, and allow the user to actuate and manually open the manual valve.