In this work, SnO₂ sensors have been used in order to detect leaks of hydrogen on a cryogenic motor. In a first part, the SnO₂ sensors performances have been evaluated on a laboratory testing bench under different hydrogen and oxygen concentrations in the nitrogen carrier gas. A particular attention has been focused on the influence of oxygen on the hydrogen response of the sensor. In a second part, a multi-sensors device has been developed for a network application. Before its use, this device has been valued with eight sensors on the laboratory testing bench. The sensors have been then located at different places on the cryogenic motor in order to monitor the distribution of the hydrogen concentrations around the motor and to establish a real cartography of this latter. The experimental results obtained with the network of sensors prove their ability to control the good functionality of the different devices of the motor.