Aerosol polydispersed, generation

DOP polydisperse aerosol is generated by blowing air through liquid dioctylphthalate (DOP) at room temperature. The approximate light scattering mean droplet size distribution of the aerosol is 99% + less than 3.0 pm and 95% + less than 1.5 pm. 

The above data were obtained in healthy adnlt volnnteers. Chua et al. (100) quantified the deposition of a polydisperse aerosol in the Inngs of eight children with cystic fibrosis (median age = 10.8 years range = 6.3-18.0 years), who breathed via the nose with a face mask and closed month on one occasion and via the oral route with a mouthpiece on another. Aerosol was generated by nebu-... 

This nozzle has been used to generate polydispersed aerosols of various organic liquids as the bulk phase. Particles in the size range of submicrometers to 20 pm were obtained. The concentration varied by less than 10% over several hours as long as the air pressure was well regulated. 

To simplify the calculations, it is assumed that the concentrations, mobilities, and other properties of the positive and negative ions are equal and that the concentrations of the tons and charged particles have reached a steady slate. We consider a group of particles of uniform size no coagulation occurs,. so a polydisperse aerosol can be treated as a set of uncoupled monodisperse particles. The rates at which ions of both signs attach to particles are assumed to be independent ol each other. In the steady state, ions are generated and destroyed at the same rate by attachment to particles. Calculations indicate that ion recombination is not an important mechanism for ion loss in the atmosphere (Bricard and Pradel, Ii966). 

Fij ure 6.13 Condensation aerosol generator The nuntber concentrations of the polydispi rsp aerosol produced in the nebuli/cr ore nearly equal to that of the monodisporsc aerosol. Each evaporating droplet from the polydisperse aerosol leaves behind a residue that serves as a nucleus for the ntonudisperse aerosol. (After Liu et al., 1966.)... 

Thus the result of particle growth in the chamber is to convert a monodisperse aerosol into a polydisperse aerosol. This is the reverse of what occurs in a condensation aerosol generator (Chapter 10). 

Similarly to all other disperse systems, aerosols may be obtained (see Chapter IV) by both dispersion of macroscopic phases and condensation [5]. Aerosols generated as a result of macroscopic phase dispersion are, as a rule, characterized by a rather low degree of dispersion and are more polydispersed as compared to aerosols prepared by condensation. Dispersion methods of aerosol generation are used to prepare various important materials. These methods include the preparation of powders by grinding of solid materials, nebulizing liquid fuel ( in order to achieve a more efficient combustion), spraying pesticides and paints, etc. In nature dispersion processes lead to the formation of dust. 

Both LaMer s and the falling film aerosol generators yield only small quantities of products. Much larger amounts of aerosols can be produced by dispersing liquids with the help of various mechanical devices, e.g. rotating disks or ultrasonic nozzles [6]. These techniques, however, usually yield aerosols with broad distribution of droplet sizes and thus lead to polydisperse systems. The dispersion aerosol generators can, consequently, be used... 

Targeting of therapeutic aerosol particles to specific airway generations is not possible because both monodisperse and polydisperse aerosols will deposit over several generations. 

Other data indicate that bronchodilator particles that are <5.6 pm are more efficacious than larger particles. Rees et al. (49) incorporated terbutaline crystals into standard MDIs and generated polydisperse aerosols characterized by three different MMADs 5.6, 9.1, and 13.6 pm. In 10 patients with asthma, they found that only the smallest aerosol (5.6 pm) significantly improved the FEVj, sG, and MEFjq. Since the two other aerosols had no significant bronchodilating ef-... 

In the second set of e qjeriments, we will test the barrier effectiveness of fabrics to polydisperse nanoparticle aerosols - of nano Ti02 and/or nano silver particles. This would provide a better simulation of the relevant occupational nano-environment - as the generated particles are likely to aggregate. 

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