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 , 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 , - 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 . <EOS>