The act of dust sampling to characterise potential hazards in the respiratory tract is a process that requires initial removal of non-inspirable particles followed by separation into regional fractions. Particles that are not inhaled cannot deposit anywhere in the respiratory system. Furthermore, there is an important category of aerosol for which the conditions for potential injury is inhalation and deposition anywhere in the respiratory tract. Thus inspirable dust sampling is fundamental to all aerosol sampling for health risk evaluation. A proper estimation of inhalation exposure will need to examine the relationship between the inspiration efficiency of a sampler and particle size distribution of a dust cloud; and methods to collect a representative sample in the workplace.