Yes, it is contagious. M.tuberculosis infection occurs due to inhalation of droplet nuclei i.e: infectious particles aerosolized by coughing, sneezing or talking. These are sufficiently small to dry while airborne, remain suspended for long periods and reach terminal air passages of the lungs.

It has been observed that a cough from an infected person produces 3000 infectious droplet nuclei. Accordingly, the air in a room occupied by him may remain infectious even during his temporary absence.