A drug is to be delivered by a nebulizer. The size of a droplet for its humidification is : (AIIMS May 2009)
Particles of size <2.5 μ can be carried to the lower airways.
1). Particles with size above 10-15 μ in diameter, because of their settling velocities in air, do not penetrate beyond the upper airways.
2). Particle of size 2.5-10 μ deposit relatively high in the tracheobronchial tree.
3). Particles of size <2.5 μ can be carried to the lower airways.