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

Abstract

Objectives 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. Methods Volumetric airflow were measured to assess air change rate per hour by ventilation (ACH vent ). Equivalent ventilation provided by the PAC (ACH pac ) 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 (K n ) and with ventilation and PAC (K n+pac ), and by times needed to reach 95 % and 100 % removal of accumulated aerosol particles. Results ACH vent varied from 3 to 45. K n and K n+pac were correlated with ACH vent (r = 0.90) and combined ACH total (r = 0.81), respectively. Accumulated aerosol particles could not be removed by ventilation alone within 30-min in rooms with ACH vent <15. PAC reduced aerosol accumulation and accelerated aerosol removal, and accumulated aerosols could be completely removed in 4 to 12-min by ventilation combined with PAC. Effectiveness of the PAC was especially prominent in rooms with poor ventilation. Added benefit of PAC in aerosol removal was inversely correlated with ACH vent . Conclusions Aerosol accumulation may occur in dental treatment rooms with poor ventilation. Addition of PAC with a HEPA filter significantly reduced aerosol accumulation and accelerated aerosol removal. Clinical significance Addition of PAC with a HEPA filter improves aerosol removal in rooms with low ventilation rates.

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