Detecting volatile organic compounds (VOCs) in exhaled breath is a promising research area for disease diagnosis. Mass transfer behavior plays a crucial role in determining the detection performance of VOCs. However, the high mobility of exhaled breath poses a substantial challenge for the mass transfer process. Here, the distinct mass transfer behavior of mobile gaseous molecules is discovered by employing the schlieren imaging technique to visualize gas flow. The results demonstrate that hollow porous structures exhibit a higher gas flow flux than solid film and microporous structures, thereby generating a sufficient probability of contact reactions for mobile gaseous molecules. The proposed colorimetric array sensors offer enhanced sensitivity and stability for detecting mobile gaseous molecules. The discovery will serve as a foundational milestone is anticipated in elucidating the behavior of gas mass transfer and promoting its potential application in disease detection through the analysis of human exhaled breath. The analysis of volatile organic compounds (VOCs) in exhaled breath is expected to be used for disease diagnosis and health monitoring. The schlieren imaging technique of gas flow is employed to elucidate the mass transfer behavior of mobile gas across various structures. The hollow porous structures significantly enhance the flux of gas transport, improving the visualized results and detected sensitivity of colorimetric array sensors CASs.