The library environment is vulnerable to fire threat due to the paper based publications it contains. Since it is a public open environment and it contains valuable resources like handwritten historical documents, it is very important to ensure the safety of life and property in libraries. Therefore, gas and smoke detection based fire detection systems are used. In this study, using wireless sensor networks, a library fire detection system has been designed and implemented on the TinyOS development platform. IRIS nodes and temperature sensors are used in the system. The designed system is tested in library environments. To the best of our knowledge, it has been reported that detection systems generate alarm in approximately 30 s, while new systems are reported to react in about 3 s. According to the results obtained, our system has reacted before 3 s. The proposed system is successful with features such as easy installation, quick alert creation and simple usage.