Suppressions of the gasoline-air mixture explosion by non-premixed nitrogen were studied experimentally in a closed tunnel. During the process of experiments, the test tunnel was divided into three parts by two plastic films: igniting section, N-2 suppression section and gasoline-air mixture section. Meanwhile, two flame intensity sensors were respectively deployed in front of and behind the N-2 suppression section. Based on the analysis of the flame intensities, overpressures and concentrations of the gas components after ignition, the gasoline vapor concentration range in which the explosions can be effectively suppressed, critical length of the ignition section and critical O-2 concentration in the suppression section were discussed in detail. It was indicated that values of maximum overpressure and overpressure rise rate of the explosions with non-premixed suppression were lower than that without such suppression. When the initial gasoline vapor concentration is constant, the critical length of the ignition section increases with the growth of the length of the N-2 suppression section. The relationship between the critical length of the ignition section and the initial gasoline vapor concentration can be described as a negative exponential expression of y = ae(-bx). There are three modes for the explosion suppression experiments: complete suppression mode, partial suppression mode and suppression failure mode. The critical O-2 concentration in the N-2 suppression section decreases with increase of the lambda (a dimensionless parameter of ignition section length/N-2 suppression section length) when the initial gasoline vapor concentration is 2.0%. (C) 2014 Elsevier Ltd. All rights reserved.