In indoor air, viable Mycobacterium tuberculosis can remain infectious for several hours. In a poorly ventilated, stagnant room the bacilli can persist for 8–12 hours and, under extreme conditions with no air exchange, may survive up to about 24 hours. In contrast, in a normally ventilated space (air changes of 6–12 per hour) the concentration drops rapidly and the risk becomes negligible within minutes to roughly an hour. Therefore, when estimating exposure risk, assume that the organism can stay alive for up to half a day in the worst‑case indoor environment, and take steps to improve ventilation, use airborne‑infection isolation, or employ UV air disinfection to shorten that survival time.
How long does viable Mycobacterium tuberculosis remain infectious in indoor air after being expelled?
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Last updated: February 28, 2026 • View editorial policy
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