Exposure to infectious bioaerosols (say in a mass transport environment) may be a health hazard to passengers and staff during pandemics or other high threat pathogen incidents. To determine the human inhalation exposure risk to airborne pathogens, it is important to estimate the airborne bioaerosol concentration near the emission source as a function of position and time. Bioaerosol dispersion indoors is a complex phenomenon which is affected by the air flows as well as the source characteristics. To calculate the bioaerosol concentrations following a short-term release an analytical model presented by Drivas et al. was used. The model takes into consideration point-source dispersion and the general concentration decay due to ventilation and particle settling. One key parameter in the model is turbulent diffusivity which is not very well known but affects crucially the calculated dispersion. Comparison of the model with experiments conducted in a large space showed that the model worked reasonably well, provided that the model parameters are correctly set. The analytical model offers a relatively simple method to estimate the inhalation exposure and thus risk for infection more accurately in indoor spaces and may be extended to incorporate surface deposition of aerosol particles.