Resent respiratory infection outbreak events, including Avian and Swine Influenza and SARS virus spread in various countries ignited a strong interest towards investigations in the area of airborne virus behavior in the ambient air. One of the most important parameters, related to airborne disease transmission is survival of disease causing microorganisms in the ambient air environment. This project investigates survival of airborne influenza virus of different sub-types at common room conditions where risk of disease due to microbial transmission could be particularly high, especially at poorly ventilated environments, where viral concentration in the air reaches significant magnitudes. The results obtained for H1N1 and H5N1 strains show close trend with regards to inactivation in the ambient air; rapid inactivation of approximately 60% of microorganisms over the first 30 min with following inactivation at much slower rate over the remaining 60 min of experiment. A different picture was observed for the H3N2 strain, which demonstrated much higher robustness compared to other subtypes; even after 90 min, around 50% of viral particles were still alive. The results of this research could be directly utilized in health and epidemiological studies, modeling of HVAC systems, microbiological studies and many others. (c) 2012 Elsevier Ltd. All rights reserved.