Fire fighters often work in dangerous and dynamic environments, which results in frequent change of network topologies and routing requirements. While the existing routing protocols are not able to cope with such a changeable environment, this paper proposes a self adaptive hybrid routing algorithm. This routing algorithm can switch between the proactive routing algorithm and reactive routing algorithm for each node pair automatically. An analytical model is created to describe the routing switch decision making algorithm. This model is based on a set of the cost functions. A numerical example shows the necessity of switching routing algorithms to reduce the overall control message overhead.