A connection device (2; 102; 202) for gas appliance, comprising: a first control member configured to be rotatably moved between a closing position and an opening position, such that: • when the first control member is in the closing position, the first control member is arranged to fluidly disconnect the connection device (2; 102; 202) for gas appliance from a gas cartridge; • when the first control member is in the opening position, the first control member is arranged to fluidly connect the connection device (2; 102; 202) for gas appliance to a gas cartridge; and a second control member configured to be rotatably moved between a locking position and an unlocking position, such that: • when the second control member is in the locking position, the second control member is arranged to lock the connection device (2; 102; 202) for gas appliance to the gas cartridge; • when the second control member is in the unlocking position, the second control member is arranged to unlock the connection device (2; 102; 202) for gas appliance from the gas cartridge, wherein the first control member and the second control member are configured such that: • when the second control member is in the unlocking position, the second control member is in vertical alignment with the first control member and prevents rotational movement of the first control member between the closing position and the opening position; and • when the second control member is in the locking position, the second control member is not in vertical alignment with the first control member and permits rotational movement of the first control member between the closing position and the opening position. a first control member configured to be rotatably moved between a closing position and an opening position, such that: • when the first control member is in the closing position, the first control member is arranged to fluidly disconnect the connection device (2; 102; 202) for gas appliance from a gas cartridge; • when the first control member is in the opening position, the first control member is arranged to fluidly connect the connection device (2; 102; 202) for gas appliance to a gas cartridge; and • when the first control member is in the closing position, the first control member is arranged to fluidly disconnect the connection device (2; 102; 202) for gas appliance from a gas cartridge; • when the first control member is in the opening position, the first control member is arranged to fluidly connect the connection device (2; 102; 202) for gas appliance to a gas cartridge; and a second control member configured to be rotatably moved between a locking position and an unlocking position, such that: • when the second control member is in the locking position, the second control member is arranged to lock the connection device (2; 102; 202) for gas appliance to the gas cartridge; • when the second control member is in the unlocking position, the second control member is arranged to unlock the connection device (2; 102; 202) for gas appliance from the gas cartridge, • when the second control member is in the locking position, the second control member is arranged to lock the connection device (2; 102; 202) for gas appliance to the gas cartridge; • when the second control member is in the unlocking position, the second control member is arranged to unlock the connection device (2; 102; 202) for gas appliance from the gas cartridge, wherein the first control member and the second control member are configured such that: • when the second control member is in the unlocking position, the second control member is in vertical alignment with the first control member and prevents rotational movement of the first control member between the closing position and the opening position; and • when the second control member is in the locking position, the second control member is not in vertical alignment with the first control member and permits rotational movement of the first control member between the closing position and the opening position. • when the second control member is in the unlocking position, the second control member is in vertical alignment with the first control member and prevents rotational movement of the first control member between the closing position and the opening position; and • when the second control member is in the locking position, the second control member is not in vertical alignment with the first control member and permits rotational movement of the first control member between the closing position and the opening position.