A simple and efficient method for evaluating air-cleaning performance against airborne allergen particles

Size- and time-dependent aerodynamic behaviors of airborne allergen particles were evaluated in a 30-m3 chamber, both with and without the operation of air-cleaning devices: a dehumidifier and an air conditioner. In-situ real-time measurements were taken using an optical particle counter. Removal efficiencies obtained from the counter, based on particle number and volumetric concentrations, were compared to values from the conventional ELISA method, which is time-consuming and requires off-line measurements. The log of clean-air delivery rates (CADR) was linearly proportional to the log of particle size. When a dehumidifier and an air conditioner were used, CADRs against airborne allergen particles increased by 4 and 7 times, respectively, compared with conditions without air-cleaning devices. The settlement of the particles smaller than 1 μm was hardly affected by gravity, but concentrations of these particles decreased to nearly 50 and 30% of the initial concentrations with the operation of a dehumidifier and of an air conditioner, respectively. Moreover, the concentration of particles with a peak size of about 5.7-μm decreased to 9 and 0.3% of the initial value after only 30 min of operation of a dehumidifier and of an air conditioner, respectively. Comparing removal performance results between analyses that used a particle counter and the ELISA method, our new simple test method, which used an optical counter and was based on total volume concentrations, could easily predict the removal efficiency of airborne allergen particles, and the results were consistent with those obtained using the ELISA method.

► A simple method is suggested for allergen aerosol removal by air-cleaning devices.
► Artificial allergen particles, an in-situ particle counter, and a chamber were used.
► Aerodynamic removal by a dehumidifier and an air conditioner was clearly discriminated.
► Removal efficiency by ELISA could be predicted by an optical particle counter.