The present invention relates to a method and apparatus for controlling a gas flow through a conjunction between one or more incoming streams and one or more outgoing streams through a conjunction. The method uses a biased mass flow imbalance value obtained by comparing the aggregate of incoming mass flow measurement value(s) with the aggregate of outgoing mass flow measurement value(s) and adding a bias component to provide the biased mass flow imbalance value. The flow of at least one of the incoming and outgoing streams (12, 14, 16, 18, 20) is adjusted to move the biased mass flow imbalance value towards zero. In addition, a conjunction pressure measurement (PC) is provided, which is used to adjust the bias component in response to a change in the conjunction pressure measurement (PC) relative to a pressure set point (PSP), to mitigate the change in the conjunction pressure measurement (PC) relative to the pressure set point (PSP).