A Multijet Aerosol Nebulizer System for Controlled Clinical Studies in Environmental Chambers

Abstract

Controlled clinical studies directed at health-related effects of air pollutants are based largely on the use of environmental chambers. Typically, such chambers are single-pass systems requiring the production of large amounts of pollutant each minute and continuing for several hours. In order to produce a stable aerosol concentration and particle size distribution for up to 8 hours without operator adjustments, we have developed a special aerosol nebulizer system. Basically, the system evolved from the single-jet Dautrebande (D₃₀) nebulizer. We designed a unit to accommodate up to eight such jets. An 8-L reservoir was provided for the aqueous solution (or suspension). Delivery of the solution to be aerosolized to the jets is accomplished by the Bernoulli effect of each air jet, thereby “lifting” the solution from the reservoir to the jet where aerosol droplet production occurs. Because the number of air jets can be varied, a factor of eight in aerosol mass output is simply achieved at the same solute concentration. Although our major experience with this nebulizer has been limited to four hour aerosol exposures (concentrations from 50 to 1000 (μ/m³), we have determined, for example, that with all eight jets operating at 138 kPa gauge (120 L/min), there was less than a 10% increase in aerosol mass concentration in our 45-m¹ chamber over an 8-hour period of unattended operation and consequently no significant change in the mass median aerodynamic diameter (0.8 μm, δ₂ 2.2). This nebulizer system is relatively inexpensive to construct and it effectively eliminates changes in aqueous solution concentration and particle size, both inherent characteristics of commercial nebulizers. We believe, therefore, that the eight-jet nebulizer system provides a simple, versatile, and reliable aerosol generation device for controlled clinical studies in environmental chambers.