Directorate of Force Health Protection Health Services Group Headquarters 101 Colonel By Drive Ottawa ON K1A 0K2 Assessment of the Effectiveness of Selected Air Cleaning Devices in Capturing Aerosols Produced During Dental Procedures Prepared by: Lt(N) J. Kriese DHHAT Leader Capt T. Maurais, CIH DHHAT Leader Reviewed by: L. Maheux, CIH DFHP Senior Industrial Hygienist LCol S. Blier, MD, MPH Head OEH DATE OF REPORT: 27 May 2020 Proprietary Notice This report contains the proprietary and confidential information of the Department of National Defence (DND) and shall not be used, disclosed or reproduced, in whole or in part, for any purpose without the prior written consent of DND. Title in and to this report and all information contained herein remains at all times in DND. No Warranty This report is provided for information purposes only without any warranty regarding the recommendations expressed herein. DND assumes no liability for any harm that may arise from the unauthorized implementation of the report's recommendations. © Her Majesty the Queen in Right of Canada as represented by the Minister of National Defence. All Rights Reserved. Executive Summary The recent COVID-19 pandemic has underscored the necessity of protecting health care providers (HCPs) against the transmission of infectious agents during dental procedures. To this end, the effectiveness of several air cleaning devices in reducing HCPs exposure to bioaerosols was investigated, separately or in combination with each other. These air cleaning devices were the MedEVAC® Chair-Side Air Extraction and the AF400® Air Purifier (AP), both from Quatro Air Technologies Inc.; the X-2580® Air Scrubber (AS) from XPOWER Inc.; a custom made, fan operated and wall mounted air filter (WMAF) intended for mobile dental clinics (MDCs); and a smaller and passive version of the latter. These investigations were performed at three locations within the Ottawa area. First at the dental operatory of the National Defence Headquarters (NDHQ) - Carling where a familiarization with the air cleaning devices took place as well as preliminary tests. This was followed by the determination of the optimal positioning of the air cleaning devices at the operatory of Montfort Dental Clinic. The latter tests, with various combinations of air cleaning devices, were repeated at a MDC at Canadian Forces Base (CFB) Uplands. During these assessments, two dental personnel, acting in the roles of Dentist and Dental Assistant, performed on a simulated patient aerosol-generating and non-aerosol generating procedures representative of typical and worst- case scenarios. For each scenario, the concentration of airborne particulate matter of 10 µm or smaller (PM 10 ) was measured using personal and ambient air monitors. The use of the MedEVAC® AP, by capturing aerosols at the source of generation, had the greatest impact on reducing exposure of dental personnel to PM 10 produced during dental procedures, despite the fact that this air cleaning device provided a capture velocity below the guideline recommended by the American Conference of Governmental Industrial Hygienists (ACGIH). This exposure was further reduced with the addition of the AF400® AP within the clinic setting and the integrated WMAF in the MDC, with PM 10 measurements often falling below background levels. Conversely, the simultaneous operation of the XPOWER X-2580® AS in the MDC, used to create a negative pressure room, reduced the MedEVAC® AP’s effectiveness in capturing aerosols. The Directorate of Force Health Protection therefore recommends the use of the MedEVAC® AP during and after dental procedures where risk of infectious agent transmission is present, in conjunction with the AF400® AP in clinic dental operatories and with the WMAF in the MDCs. Where feasible in clinic dental operatories, maintaining a negative pressure and installing High Efficiency Particulate Air (HEPA) filters in exhaust outlets in order to reduce aerosol migration outside of the operatory are also recommended. The operation of the XPOWER X-2580® Air Scrubber is not recommended during dental procedures in MDCs as air movements decreased the effectiveness of the MedEVAC® AP. Keeping the air cleaning devices functioning after performing dental procedures requiring the use of the MedEVAC® AP, waiting time periods should be adopted before leaving the room (10 minutes in clinic dental operatories; 3 minutes in MDCs) and before reentering the room (an additional 20 minutes in clinic dental operatories, and an additional 5 minutes in MDCs). Standard operating procedures (SOPs) should be developed to ensure the optimal utilization of air purification systems as determined in this report. 1 © Her Majesty the Queen in Right of Canada as represented by the Minister of National Defence. All Rights Reserved. Table of Contents Page 1 Background and Rationale ......................................................................................................4 2 Applicable Guidelines and Standards .....................................................................................6 2.1 Selected Size of Aerosols to Sample ................................................................................6 2.2 Required Capture Velocity ...............................................................................................6 2.3 Required Aerosol Removal Efficiency before Exiting and Reentering Operatory ...........7 2.4 Room Differential Pressure...............................................................................................8 2.5 Air Changes per Hour .......................................................................................................8 2.6 Air Exhaust .......................................................................................................................8 3 Methodology ...........................................................................................................................9 3.1 Determination of the Optimal Position of the MedEVAC® AP Flange ..........................9 3.2 Personal and Ambient Air Sampling of PM10 during Dental Procedures .......................9 3.3 Calculation of the Effectiveness of the MedEVAC® AP in Capturing PM 10 ................10 3.4 General Ventilation Assessment .....................................................................................10 3.5 Assessment at NDHQ Carling Dental Clinic Operatory .................................................10 3.6 Assessment at Montfort Dental Clinic Operatory ...........................................................11 3.7 Assessment in a Mobile Dental Clinic ............................................................................12 4 Results ...................................................................................................................................13 4.1 Air Changes per Hour and Differential Pressures...........................................................13 4.2 NDHQ Carling Dental Clinic Operatory ........................................................................14 4.3 Montfort Dental Clinic Operatory ..................................................................................16 4.4 Mobile Dental Clinic at CFB Uplands ............................................................................22 4.5 Estimated Effectiveness of the MedEVAC® AP under Various Conditions .................24 5 Discussion .............................................................................................................................25 5.1 Room Differential Pressures ...........................................................................................26 5.2 Air Exhaust .....................................................................................................................27 5.3 Effectiveness of the Assessed Air Cleaning Devices .....................................................27 5.4 Dental Procedures and Peaks of Generated Aerosols .....................................................28 5.5 Air Cleaning Devices Limitations and Appropriate Controls .........................................28 5.6 Waiting Periods before Exiting and Reentering Clinic Dental Operatories and MDCs ...................................................................................................29 5.7 Limitations ......................................................................................................................29 6 Conclusions ...........................................................................................................................30 7 Recommendations .................................................................................................................31 8 References .............................................................................................................................32 Appendix A – Time-Weighted Averages (20 sec.) Concentrations of PM10: Montfort ............34 Appendix B – Time-Weighted Averages (20 sec.) Concentrations of PM10: MDC .................38 Appendix C – Calculated Duration before Exiting and Reentering a MDC ...............................41 2 © Her Majesty the Queen in Right of Canada as represented by the Minister of National Defence. All Rights Reserved. Abbreviations and Acronyms ACGIH American Conference of Governmental Industrial Hygienists ACH Air Changes per Hour AGPs Aerosol-Generating Procedures AP Air Purifier AS Air Scrubber CAF Canadian Armed Forces CDC U.S. Centers for Disease Control and Prevention CFB Canadian
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