Gas injection control devices are provided, particularly for deployment in a well-bore to control injection of a gas into a tube or pipe to lift a liquid up the tube, such as crude oil for example. A gas control device is described which comprises a housing, and at least two control valve arrangements within the housing. Each arrangement has an inlet for receiving gas from a pressurized supply, an outlet for supplying pressurized gas for injection into the tube, an inlet valve in a fluid path between the inlet and outlet, and an actuator associated with the inlet valve. Each actuator is independently controllable to switch the respective inlet valve between its open and closed configurations. This allows the gas injection to be switched on and off, and facilitates control of the injection gas flow rate.