Most laser techniques are not capable of examining the entire aerosol. This means that the sampling technique must be included in the interpretation of the data obtained. Isokinetic sampling is imperative, and sampling conditions must, therefore, be considered of the utmost importance . During the measurement of the particle size by this method, the aerosol does not encounter an impaction surface as is the case during inhalation. Thus, the assignment of a particle size representing the nominal cutoff for the respirable fraction does not have the same meaning as the same size in inertial sizing systems. It is likely that some of the small particles are removed from the airstream in the upper airways by aggregation, droplet coalescence, and impaction. This is not mimicked by the laser technique. The laser technique will, however, give some insight into droplet dynamics during passage from the actuator. Therefore, it is possible to investigate the size as a function of the time after leaving the actuator, which will result in information concerning the dynamics of evaporation and aggregation effects.
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If you suffer with asthma, you will no doubt be familiar with the uncomfortable sensations as your bronchial tubes begin to narrow and your muscles around them start to tighten. A sticky mucus known as phlegm begins to produce and increase within your bronchial tubes and you begin to wheeze, cough and struggle to breathe.