<prompt> A drug is to be delivered by a nebuliser. The size of a droplet for its humidification is :5m10-May15-Oct15-20  <response>: Answer is A 5 m: Paicles of size 2.5 mm can he carried to the lower airways. Paicles with size above 10-15 mm in diameter, because of their settling velocities in air, do not penetrate beyond the upper airways Paicle of size 2.5-10 mm deposit relatively high in the tracheobronchial tree. Paicles of size 2.5 mm can be carried to the lower airways. 