This research took the breathing microenvironment as the object to conduct an analysis on personal exposure risk in the human breathing process under the effect of the limited space air stability by means of a full-scale experiment and numerical simulation. The results showed that the personal exposure level mainly depended on the breathing activity during the pollutants initial releasing period. As the pollutants went further， the influence of limited space air stability and ventilation on personal exposure became important and presented a characteristic of time independence. In the stable condition， due to the lock-up effect of the stratified environment， the transport of the exhaled pollutants tended to remain in the initial inertia force direction， and not easy to spread； The unstable condition was more likely to disturb the ability of the initial inertia force transport direction and to accelerate the diffusion of pollutants， thus greatly reducing the personal exposure in the breathing microenvironment. This study has theoretical and practical significance in controlling the transport of pollutants， preventing the spread of disease， and ensuring occupant health.