Wireless sensor networks are dependent on signal sending and receiving; the system will not be able to function if communications between sensors are not established. In this paper, the use of sub-networks in randomly distributed nodes converts the network from a random distribution to an organized one and saves operation time and energy per node. It was found out that using coverage sub-networks by dividing the network into three sub-networks with operation time of 10 minutes per sub-network every 30 minutes increases the network life time by 2.7% and increases the energy performance by 63% as compared to normal fire detection networks.