There are no special difficulties in solving network ventilation problems with the aid of computing techniques. A large number of methods has been devised for solving them with computers and analog machines; these have often been surveyed in the Soviet literature and therefore we shall not discuss them here. We will describe the need for devising a new methodological approach for solving a special group of ventilation problems, and suggest a general method for solving them. If the ventilator fans or passive elements are incorrectly chosen, a situation may arise in which the aerodynamic conditions of one or more fans cross from the operational to the nonoperational branches of their characteristics. There is then a sharp depression of the fan. Such a situation is called unstable operation of the fans. It is regarded as an emergency, because in this case the ventilation conditions are ineffective and normal operation of the ventilator fans is impossible. If the characteristic of the ventilator fan is superimposed on the corresponding characteristic of the network, their points of intersection will determine the possible conditions of operation of the fan. If there is only one point of intersection, the conditions are single-valued, i.e., stable; if theremore » are several points of intersection, then they are many-valued, and thus unstable. This is the only condition of stability. However, there can be various methods of verifying the satisfaction of this condition. There are two known methods of testing for stability: by plotting complete aerodynamic characteristics of the network at the points of installation of the ventilators, and by means of criteria of stability. We devise a new universal method of testing for stability in networks of any degree of complexity suitable for any method of computation. The principles of this method are described.« less