Summary

Several stable methods of aerosol generation have been discussed. Their characteristics are summarized in Table 1. Commercial sources of these generators are listed in Table 2. These methods are suitable for aerosolizing bulk materials that are either liquids or powders. Solids can be converted to a liquid by the use of solvents or to a powder by grinding. The generators listed in Table 1 offer methods of producing polydisperse and monodisperse aerosols. Each method has certain characteristics that may be suited for a particular application. The electrostatic classifier and the vibrating-orifice and spinning-disk generators produce monodisperse aerosols. The evaporation-condensation generator can also produce monodisperse aerosols under controlled conditions. The vibrating-orifice and spinning-disk generators are usually used for producing micrometer-size particles, whereas the other monodisperse generators are used for submicrometer-size particles. Polydispersed particles are generated by nebulizers and evaporation-condensation generators. The dust-resuspension generators listed in Table 1 produce aerosols at different rates. Low stable output is best achieved by a small fluidized-bed generator, although equilibration time may be long. Improved equilibration time and higher output are characteristic of the air-impaction type of dust generators. However, the stability is controlled by the packing of the power column.

The usual constraints for using these generators are that the liquids be sufficiently inviscid and that the powders be noncohesive. In the case of liquids

Table 1 Comparison of Aerosol Generation Methods

Parameter

Coping with Asthma

Coping with Asthma

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.

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