The present invention relates to deriving and utilizing content signatures. When the detected current value falls in the range between the upper and the lower limit values after execution of the forward control, a reverse control is executed such that a pulse width of a PWM signal is changed in an adjustment direction opposite to that under the forward control. In a data base, the side lengths of each distinctive triangle is referenced to the part it identifies and to related processing parameters. The ventilation stream, alternatively, can be induced by operation of a fan driven by a motor which operates independently of the operation of the oxidant delivery system. The container is a sealed canister, such as a bag or jug, which is preferably impermeable to light.