Indoor particle concentrations associated with use of tap water in portable humidifiers
A study was conducted in Boise, ID, residences to investigate the impact on indoor air quality of using tap water in portable home humidifiers. Commercially available units tested with tap water of known dissolved solids content included ultrasonic, impeller, and steam. Samples were collected for gravimetric analysis along with information on temperature, relative humidity, and airexchange rates. Fine particle concentrations measured in the bedroom of one residence were greater than 590 pg/m3 when an ultrasonic humidifier was operated in the kitchen using tap water containing 303 mg/L total dissolved solids. Fine particle concentrations in excess of 6300 pg/m3 were observed when the ultrasonic humidifier was operated in a closed room situation. The impeller units generated less than one-third the aerosol mass generated by the ultrasonic humidifiers. A steam unit generated no measurable increase in PM 10-.