This paper presents a novel disposable breath-sensing tube with an on-tube single-nanowire (NW) sensor array for noninvasive, simple, and on-site detection of exhaled breath biomarkers. Although various noninvasive detection methods for lung cancer biomarkers in breath samples exist, they are unsuitable for self-diagnostics and immediate detection because they entail complicated handling procedures and are time intensive. In this study, we simulated, fabricated, and characterized disposable nanosensors by using single TiO2 and Ag NWs in flexible plastic tubes. The proposed sensors simultaneously detect 2-propyl-1-pentanol (2-PP) lung cancer biomarkers and changes in the humidity, flow rate, and temperature of the flowing gas. The optimal dimension of the tubes was determined and verified through dynamic simulations and experiments. The current tube design decreases sensing variation and moisture interference by 43.28% and 78.77%, respectively, compared with previous designs. In the future, the proposed breath sensor, which has a response time of less than 10 s, can be used in a tube for simple and quick screening of lung cancer patients with the 2-PP concentration exceeding 100 ppb. The developed breath-sensing platform can be applied in noninvasive on-site disease screening.