Size and mineral composition of airborne particles generated by an ultrasonic humidifier

• Published in: Indoor air Vol. 28; no. 1; pp. 80 - 88
• Main Authors: Sain, A. E., Zook, J., Davy, B. M., Marr, L. C., Dietrich, A. M.
• Format: Journal Article
• Language: English
• Published: England Hindawi Limited 01.01.2018
• Subjects: air quality; air‐water interface; Exposure; Humidification; humidifier; Humidifiers; Humidity; Inhalation; inhalation exposure; Inhalation Exposure - analysis; Mineral composition; Mineral waters; Minerals; Minerals - analysis; Particle Size; Particle size distribution; PM2.5; Respiration; Size distribution; Spatial Analysis; Time Factors; Water - chemistry; Water quality; air-water interface; humidifier; water quality; PM2.5; inhalation exposure; air quality
• ISSN: 0905-6947; 1600-0668
• DOI: 10.1111/ina.12414

This study describes the size distribution and concentration of particles expelled by a portable, 3‐L ultrasonic humidifier. The ultrasonic humidifier was filled with waters of varying mineral content and hardness. Aerosol size distributions were measured during 8 hours of humidifier operation in a typical bedroom. Humidifiers produced approximately 1.22 × 1010‐2.50 × 1010 airborne particles per milliliter of water consumed, resulting in airborne particle concentrations of 3.01‐5.91 × 104 #/cm3, with modes ranging between 109 and 322 nm in diameter. The emission rate of particles varied by water type from 1.02 × 109 to 2.27 × 109 #/s. Lower mineral waters produced fewer, smaller particles when compared to higher mineral waters. Chemical analyses of particles collected with a cascade impactor indicated that the minerals in emitted particles had the same relative mineral concentrations as the fill water. Our results demonstrate that ultrasonic humidifiers should be considered a source of inhalation exposure to minerals dissolved in water, and that the magnitude of exposure to inhalable particles will vary with water quality.