Nowadays Chemical, Biological, Radiological and Nuclear (CBRN) agents are real threats, and they can be released from intentional and non-intentional sources. Intentional sources include weapons of mass destruction, and they can inflict serious amount of damage. CBRN non-intentional sources can go from disease outbreaks or even incidents, such as a nuclear accident. The interest for unmanned vehicles is growing more and more, either in military or civilian applications. In this scenario, they can be applied, especially Unmanned Aerial Vehicles (UAVs). The response to CBRN releases should follow several steps, such as reconnaissance of the affected area, detection of the agent, sampling, decontamination, victim screening, medical evacuation, identification of the type of agent and medical treatment. Therefore, UAVs can be an important asset in this scenario, as they bring many advantages, such as the access to inhospitable or inaccessible spaces, incorporation of sensors that can be used to identify the agent, and many other factors that increase the speed of the task, reducing at the same time the risk to personnel. In this paper, an UAV system is presented to fulfill the requirements of this issue, including the vehicle, sensors and control station. This system was tested and the validation tests are also represented. It proved to be an asset in CBRN releases, either intentional or non-intentional.