In this paper is characterized experimentally a closed parking to obtain an empirical propagation model of radio waves at 900 Mhz and identify the conditions and settings required for the assembly and installation of a carbon monoxide, humidity and temperature monitoring system, using IEEE 802.15.4/ ZigBee protocol. From the experimental data, was found that the Path-Loss model evidencing the best performance. Knowing this model allows to establish the number and optimal placement of network nodes. According to the obtained results, each node should be on average 30m spacing and characterized parking would require 4 nodes to establish the network.