A first reset switch is attached to a combustion controlling device. A second reset switch is installed at a remote place distant from the combustion controlling device. A first reset input from the first reset switch is received without any restriction to release the lockout. A reset input from the second reset switch is received with any restriction to release the lockout. Specifically, when the lockout releases are performed for a predetermined number of times or more upon receiving the reset input before a predetermined time elapses after the lockout has been released upon receiving the initial reset input, the release of the lockout upon receiving the reset input is prohibited until the predetermined time elapses.