All nebulisers have a residual volume, this is due to the design requirements of the systems. A certain residual volume is always remains in the nebuliser. This is taken into account when medication dosing is calculated by clinicians and drug companies.
Please note that you should stop inhaling as soon as you hear a clear change in the sound the nebuliser makes (from a quiet, smooth hiss to a bubbling or crackling noise) and the aerosol aerosol
An aerosol is a colloid of fine solid particles or liquid droplets, in air or another gas. mist escapes from the nebuliser irregularly.