This paper presents a nonlinear model and a control strategy to regulate airflow in small-scale underground mine ventilation networks. In underground ventilation control systems, a sensor and an actuator for each branch are usually considered. However, in small-scale underground mines, it is too expensive to have automatic doors for controlling the air flow in each tunnel, as well as to install flow and gas sensors in each branch. In order to regulate airflow in small-scale underground ventilation networks, the number of sensors and actuators is regarded as a limitation for practical installation. This work presents an alternative modeling of the network, with direct control of the airflow in each tunnel, by varying the speed of the fans available on the external surface of the mine. A state space model is presented, and a linear quadratic controller with integral action and a state estimator is designed. To validate the model and the controller, a network ventilation system for a small-scale mine with nine branches (tunnels) and two actuators (fans) is presented.