Addition of PAC with HEPA filter may prevent COVID-19 spread in dental clinics: Study
Researchers from the Eastman Institute for Oral Health, University of Rochester Medical Center, Rochester, New York, USA have said that aerosol accumulation may occur in dental treatment rooms with poor ventilation. Addition of portable air cleaner (PAC) with a HEPA filter will significantly reduce the aerosol accumulation and accelerated aerosol removal, as documented in the recent study published in the Journal of Dentistry.
Yan-Fang Ren and colleagues, therefore conducted the study 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 was 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.
It was observed that –
a. ACHvent varied from 3 to 45. Kn and Kn+pac were correlated with ACHvent (r = 0.90) and combined ACHtotal (r = 0.81), respectively.
b. Accumulated aerosol particles could not be removed by ventilation alone within 30-min in rooms with ACHvent<15.
c. 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.
d. Effectiveness of the PAC was especially prominent in rooms with poor ventilation.
e. Added benefit of PAC in aerosol removal was inversely correlated with ACHvent.
Hence, the authors concluded that the "addition of PAC with a HEPA filter improves aerosol removal in rooms with low ventilation rates."
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