Aerosol number and mass distributions produced by an ultrasonic room humidifier and an ultrasonic medical nebulizer were examined in a limited-scale study. Rapid droplet drying occurred at room humidities and under near saturated conditions. A model was tested describing the diameter of dried particles as a function of the dissolved mineral content of the water and the transducer frequency. Water containing 102 mg/L of dissolved minerals in a humidifier with a 1.6 MHz transducer produced droplets with a mass median diameter of 2.9 μm. The number median diameter of particles after drying was computed to be 0.11 μm. The distribution of particles in a nebulizer tube using a NaCl solution was shown to consist of a mixture of dried salt particles and droplets which included coagulated multiplets.
Bibliographical noteFunding Information:
The guidance of David Leith and Parker Reist and the technical input of Rich Kamens and Russ Wiener are gratefully acknowledged. This work was partially supported by U.S. Environmental Protection Agency cooperative agreement CR815152 with the University of North Carolina.
Copyright 2016 Elsevier B.V., All rights reserved.