Detection and controlling of leaks of poisonous gases such as H₂S gas in industrial workplaces have drawn the attention of many researchers. In this study, we have used quad-copter Drone (UAV) of 1200 g to detect the leak of H₂S gas in one of the refineries in Iraq. The drone is equipped with many components including, but not limited to, global positioner system (GPS), and a hydrogen sulphide H₂S sensor to detect the concentration of this dangerous gas in oil refinery facilities. It has four DC motors, and a battery. It flies fifty minutes before replacing the battery with a charged one. The drone has been customized utilizing mission planer or/and Arduino programming. The administrator controls the system by using radio frequency of a remote control. The estimating of the concentration of H₂S gas is performed by utilizing MQ sensors connected with the drone. Ten positions were selected in order to test the concentrations of H₂S gas, and all values were found in the range of 1.058–5.034 which are considered to be within the allowable limits. The methodology of this study is composed of hardware and software programming through the Arduino Uno. The result indicates that this technology is capable to protect the life of personnel in oil and gas facilities and consequently, this proposed method is promising and could be the basis of further research in this area.