For a respirator to protect against airborne M. tuberculosis droplet nuclei it must be capable of filtering a particle 0.3 μm in diameter. Respirators are special types of masks that usually have a minimum filter efficiency of at least 95% for particles of 0.3 μm in diameter.
There are different kinds of respirators and two classification systems for them, the US system and the European system (see the table here).
Both provide adequate levels of filtration and choosing one over the other will depend on availability, the structure of the user‘s face and their cost.
