||A new finite source queueing model is introduced in order to calculate the most important system performance characteristics (e.g. mean waiting time, mean number of requests waiting for transmission). The sensors are classified according to their working purposes: The first class is the "Emergency" class, which is responsible to notify special emergency situations (e.g. fire alarms). The second class is the "Standard" class, which performs the measurement of standard environmental data (e.g. humidity). The novelty of this investigation is the introduction of servers vacation combined with priority customers for finite-source retrial queues and its application to wireless sensor networks.