Respiratory tract biological particulates

Airborne particles can be classified and characterised in a number of ways and, for example according to their physical, chemical or biological properties. Also, many different terms are used in relation to airborne particles. Some of them identify particles by their sizes, others by the processes which led to their generation and some by the abihty of the particles to enter the human respiratory tract [6,7]. In particular, an aerosol is an assembly of liquid or sohd particles suspended in a gaseous medium long enough to enable observation or measurement, and a particle or particulate is a small, discrete object. 

Clearance mechanisms are different at different locations in the respiratory tract and also depend on the nature of the deposited foreign body (i.e., the physical, chemical, and biological properties of the particulate matter). 

---