<prompt> A drug is to be delivered by a nebulizer. The size of a droplet for its humidification is:5 u10-May15-Oct15-20  <response>: Because of their settling velocities in air, paicles 10-15 mm in diameter do not penetrate beyond the nose and throat. Paicles 10 mm in size are deposited below the larynx. These paicles are divided into three size fractions on the basis of their size characteristics and sources. Paicles 2.5-10 mm coarse-mode fraction contain crustal elements such as silica, aluminum, and iron. These paicles mostly deposit relatively high in the tracheobronchial tree. Ref Harrison 19th edition pg 1688 