Removal of domestic airborne dust particles by naturally charged liquid sprays

Exposure to indoor particulate pollutants and allergens has been associated with recent increases in the prevalence of allergic diseases like asthma. Reducing exposure to these particles can play an important role in prevention and abatement of asthma symptoms. A spray of fine water droplets is a well-known method for removing airborne particles. This paper presents evidence to show that the fine sprays produced by domestic pressure-pack dispensers deplete the concentration of dust particles, and when these sprays are charged, particle depletion is significantly improved. Using an air particle counter to quantify particle concentrations, comparisons were made of the rate of particle depletion by liquid aerosols with the rate at which settling occurred through natural processes alone. A standard spray from a pressure-pack dispenser with a charge-to-mass ratio (q/m) of 14 muC/kg was compared with a naturally charging equivalent with a q/m of 140 muC/kg. The standard aerosol removed up to 62% of dust particles, while the charged equivalent removed up to 78% within 90 s of spraying. The sprays differed slightly in their droplet size distributions, the charged spray comprising droplets with a volume median diameter (VMD) of 42 mum and the standard spray having a VMD of 35 mum. Comparing uncharged sprays we also measured a trend for small droplets (VMD 26 mum) to deplete particle concentration more efficiently than a spray with larger droplets (VMD = 36 mum). Thus, despite the charged spray having slightly larger droplets, the electrostatic charge resulted in more effective airborne particle removal than uncharged sprays. The use of domestic pressure-pack sprays, of the type used as room fragrance sprays, offers an inexpensive and convenient method of removing airborne dust and associated allergens in the home. This would be of particular benefit following domestic activities that entrain airborne dust. (C) 2003 Published by Elsevier Science B.V.