Magnetite (Fe3O4) nanostructures and their modifications with other materials show proper characteristics to be implemented as a sensing material. This paper provides a brief review of the application of the Fe3O4 nanostructures and their modifications as sensitive material for pollutant gas sensors. Several studies were highlighted to explain the past-to-present progress of materials development. Various synthesis procedures of the materials were also clearly explained. The application of pure Fe3O4 nanostructures and their modification as sensitive materials in gas sensor devices to detect toxic gases is the main section of this paper. Last, the future prospects section summarized the materials' development and provided a suggestion for future development.