<p>Granular materials are ubiquitous in daily life and industrial processes, playing key roles in natural phenomena and disasters. These materials consist of discrete solid particles whose flow behavior is influenced by external conditions, including ambient pressure. While the impact of gas-phase interactions on granular flows has been extensively studied in industrial applications, their role in geological disasters, such as landslides, avalanches, and debris flows, remains less explored. This review highlights the influence of ambient pressure and interstitial gases on the flow properties of granular materials, particularly in low-pressure environments such as high-altitude regions and extraterrestrial bodies. We explore the theoretical and experimental advancements in understanding gas–solid interactions and their implications for natural hazard prediction and risk assessment. Additionally, we examine state-of-the-art computational models, particularly CFD-DEM, to study gas–solid coupling in granular flows. Finally, we identify knowledge gaps and propose future research directions to improve our understanding of granular flow dynamics under extreme environmental conditions.</p>