Effects of mechanical ventilation and portable air cleaner on aerosol removal from dental treatment rooms

To evaluate the mechanical ventilation rates of dental treatment rooms and assess the effectiveness of aerosol removal by mechanical ventilation and a portable air cleaner (PAC) with a high-efficiency particulate air (HEPA) filter. Volumetric airflow were measured to assess air change rate per hour by ventilation (ACHvent). Equivalent ventilation provided by the PAC (ACHpac) was calculated based on its clean air delivery rate. Concentrations of 0.3, 0.5 and 1.0 μm aerosol particles were measured in 10 dental treatment rooms with various ventilation rates at baseline, after 5-min of incense burn, and after 30-min of observation with and without the PAC or ventilation system in operation. Velocities of aerosol removal were assessed by concentration decay constants for the 0.3 μm particles with ventilation alone (Kn) and with ventilation and PAC (Kn+pac), and by times needed to reach 95 % and 100 % removal of accumulated aerosol particles. ACHvent varied from 3 to 45. Kn and Kn+pac were correlated with ACHvent (r = 0.90) and combined ACHtotal (r = 0.81), respectively. Accumulated aerosol particles could not be removed by ventilation alone within 30-min in rooms with ACHvent