In order to properly conserve the historical documents it is critical to continuously measure some parameters, such as temperature, relative humidity, light and, also, pollutants, either in repository or bookrack rooms. The deployment of a Wireless Sensor Network in a library can help implementing these measurements in real-time, continuously, and in a much easier and cheap way. In this paper, we present a practical testbed deployed in the Hunan library, located in Changsha, China. This work is being developed in the context of an ongoing project on library environmental and structural monitor...