The current study and discussion in detail about the use of different types of porous media and barriers inside solar air heaters is our goal in this survey paper. The effect of different barriers and porous materials of different shapes and types within the solar air collectors and the effect of engineering parameters on heat transfer procedures and fluid movement were discussed by examining their thermal and hydraulic performance. Numerical and experimental analyses were presented on different types of flat solar air collectors containing differently shaped baffles or various porous media with different strategies to enhance heat transfer such as fluid flow measurement, pressure drop control, and checking their thermal and hydraulic performance by measuring the increase in air temperature at intensity Solar radiation and fluid mass flow. Studies show that the presence of porous barriers or media enhances the heat transfer process and increases the efficiency of solar air collectors. The types different of solar air collectors have been shown. We concluded this review to present various applications of solar air collectors such as cooling and heating various buildings, heating air for combustion processes, and drying coal and paper.