DFHP Assessment of Air Cleaning Devices for Dental Procedures

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.

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 Forces Base CFM Cubic Feet per Minute DFHP Directorate of Force Health Protection FPM Feet per Minute HCPs Health Care Providers HEPA High Efficiency Particulate Air HVAC Heating, Ventilation, and Air Conditioning HVE High-Volume Evacuation MDC Mobile Dental Clinic NAGPs Non-Aerosol-Generating Procedures NDHQ National Defence Headquarters PHAC Public Health Agency of Canada PM 10 Particulate Matter of 10 µm in size and smaller RCDC Royal Canadian Dental Corps SOPs Standard Operating Procedures SWMAF Small Wall-Mounted Air Filter UVGI Ultraviolet Germicidal Irradiation WMAF Wall-Mounted Air Filter

3 © Her Majesty the Queen in Right of Canada as represented by the Minister of National Defence. All Rights Reserved. 1 Background and Rationale The recent COVID-19 pandemic has underscored the necessity of protecting health care providers (HCP) against the transmission of infectious agents during dental procedures. Recognizing that dentistry is one of the highest risk healthcare fields for the transmission of infectious disease to HCPs, the Royal Canadian Dental Corps (RCDC) has already implemented robust clinical directives to mitigate the risk of transmission of COVID-19, which includes limiting the use of aerosol-generating procedures (AGPs). However, this posture hampers access to care for Canadian Armed Forces (CAF) members and to address this, the RCDC has been working with the industry, the Directorate of Force Health Protection (DFHP) and the Assistant Deputy Minister (Material) team to develop a new capability that will enhance the ability to safely treat emergency and urgent dental conditions where AGPs cannot be avoided. RCDC therefore mandated DFHP to conduct an assessment of the effectiveness of selected air cleaning devices in capturing bioaerosols. This assessment was performed: - on 9 April 2020 in a dental operatory at the National Defence Headquarters (NDHQ) Carling Campus Dental Clinic (1 Dental Unit Detachment Ottawa) by Capt T. Maurais, CIH; Luc Maheux, CIH; and WO A. Girardin, CPHI(C); where a familiarization with the air cleaning devices took place as well as preliminary testing;

- on 22 April 2020 in a dental operatory at the Montfort Dental Clinic (1 Dental Unit Detachment Ottawa) by Lt(N) J. Kriese; Capt T. Maurais, CIH; and Sgt J.P. Tessier- Guay. Various configurations of the air cleaning devices, to include different positioning of flanges, were assessed to obtain maximum aerosol removal in a clinic dental operatory setting; and

- on 23 April 2020 in a Mobile Dental Clinic (MDC) at Canadian Forces Base (CFB) Uplands by Lt(N) J. Kriese; Capt T. Maurais, CIH; and Sgt J.P. Tessier-Guay, to determine the optimal configuration of selected air cleaning devices in the MDC. All the air cleaning devices assessed used solely filtration to remove aerosols, mainly through High Efficiency Particulate Air (HEPA) filters. The MedEVAC® Chair-Side Air Extraction unit (Picture 1), from Quatro Air Technologies Inc., can be used to capture at the source aerosols generated during dental procedures. The unit is made of a 2-inch pre-filter for large particles followed by a 6-inch HEPA filter, which can be replaced by 3x 2-inch HEPA filters. This air cleaning device is intended to be used by RCDC in both clinic dental operatories and in MDCs.

Picture 1. MedEVAC® Chair-Side Air Extraction unit, from Quatro Air Technologies Inc, with extended arm attached to a clear plastic 8-inch conical flange. The MedEVAC® Air Purifier (AP) is intended to be used, depending on locale, in conjunction with some of the following to capture aerosols from the ambient air (Picture 2): - the AF400® AP from Quatro Air Technologies Inc. This air cleaning device contains the same filters than the MedEVAC® AP; - a portable XPOWER X-2580® Air Scrubber (AS); intended to be used to exhaust air and create a negative pressure room in the MDC. This unit contains a 4-stage filtration system including activated carbon and HEPA filters; - a custom-made Wall-Mounted Air Filter (WMAF) connected to the MDC Heating, Ventilation, and Air Conditioning (HVAC) system. This 2 ft x 2 ft fan operated unit contains a pre-filter and a 11.5-inch HEPA filter; and - a passive (i.e. no integrated fan) and smaller version of the latter (SWMAF; at the MDC only; not shown).

Picture 2. AF-400® AP (A), XPOWER X-2580® AS (B), and WMAF HVAC system (C). Table 1 indicates the filtration airflows provided by the various air cleaning devices assessed. These airflows were measured with the TSI VelociCalc®.

5 © Her Majesty the Queen in Right of Canada as represented by the Minister of National Defence. All Rights Reserved. Table 1. Filtration Airflows of the Air Cleaning Devices Assessed. Air Cleaning Device Airflow (CFM) MedEVAC® AP 150 AF400® AP 300 XPOWER X-2580® AS 300 WMAF 1080 SWMAF 480

The intended purpose of such an air purifying system is to decrease the risk of exposure of Dental Personnel to SARS-CoV-2 during the provision of emergency dental care to patients known or suspected of being infected by the virus. In the MDC, the combination of the WMAF HVAC system and the X-2580® AS unit is intended to create a negative pressure room relative to the outside, while filtering particulate matter.

2 Applicable Guidelines and Standards Because of the interrelation of air cleaning devices and general ventilation systems on air quality, parameters affecting both engineering controls will be covered in the current assessment. 2.1 Selected Size of Aerosols to Sample Aerosols are categorized based on their particle size: droplet nuclei (≤ 10 µm), droplet ( ≤ 50 µm), and spatter (>50 µm) . The majority (90%) of aerosols produced in dental settings are smaller than 5 µm [1]. They can contaminate surfaces in a range of 3 feet and may remain airborne for 30 minutes to 2 hours [2, 3]. Droplets also remain suspended in the air until they evaporate, leaving droplet nuclei that contain bacteria and viruses [2, 3]. Spatter will fall until it contacts other objects. Consequently, Particulate Matter 10 µm (PM 10 ; particulates of 10 µm in size and smaller) were the selected aerosols to sample for this assessment. This particle size is among those that can be sampled for by DFHP equipment (PM1.0, PM2.5, PM10, respirable particulates and total particulates). 2.2 Required Capture Velocity The American Conference of Governmental Industrial Hygienists (ACGIH) recommends different ranges of capture velocity based on the energy of dispersion of the aerosols (Table 2) [4]. Though it is understood that the velocity of bioaerosols generated during dental procedures may have a certain initial velocity, the majority quickly become suspended in the air in the vicinity of the patient’s head [2]. Furthermore, as opposed to many industrial processes generating aerosols, those produced during dental procedures only cover 180 degrees (out of the patient’s mouth), so that no energy is required to capture particles travelling opposite to the capturing airflow. Therefore, the selected guideline was a capture velocity of 100 feet per minute (fpm) based on Table 2.

6 © Her Majesty the Queen in Right of Canada as represented by the Minister of National Defence. All Rights Reserved. Table 2. Recommended Capture Velocities by ACGIH.* Energy of dispersion Examples Capture velocity (fpm)

Little motion Evaporation from tanks, degreasing 75-100

Average motion Intermittent container filling; low speed conveyor transfers; welding; plating 100 -200

High Barrel filling; conveyor loading; crushers 200-500

Very High Grinding; abrasive blasting; tumbling 500-2000 Factors affecting choices within ranges Strength of cross-drafts due to makeup air, traffic, etc. Need for effectiveness in collection: toxicity of contaminants produced by the source; exposures from other sources; and quantity of air contaminants generated. *Reproduced from [4]. 2.3 Required Aerosol Removal Efficiency before Exiting and Reentering the Dental Operatory As indicated by the Public Health Agency of Canada (PHAC), before using the room for another patient and to prevent transmission of infection, sufficient time should be allowed for the air to be free of aerosolized droplet nuclei upon completion of dental procedures [5]. While PHAC indicates that the duration will depend on the rate of air exchange in the room and provides an appendix with the aerosol removal efficiencies based on Air Changes per Hour (ACH) and the time elapsed after aerosol generation has stopped (Table 3), there is no specific level (%) recommended. The lowest values indicated are however for a removal efficiency of 90%. Table 3. Air Changes per hour and time in minutes required for removal efficiencies of 90%, 99% and 99.9% of airborne contaminants.* Minutes required for each removal efficiency Air Changes per hour 90% 99% 99.9% 1 138 276 414 2 69 138 207 3 46 92 138 4 35 69 104 5 28 55 83 6 23 46 69 7 20 39 59 8 17 35 52 9 15 31 46 10 14 28 41 11 13 25 38

7 © Her Majesty the Queen in Right of Canada as represented by the Minister of National Defence. All Rights Reserved. Minutes required for each removal efficiency Air Changes per hour 90% 99% 99.9% 12 12 23 35 13 11 21 32 14 10 20 30 15 9 18 28 16 9 17 26 17 8 16 24 18 8 15 23 19 7 15 22 20 7 14 21 *Reproduced from [5]. Therefore, considering the above Table and PHAC guidance, after the completion of a dental procedure requiring the use of the MedEVAC® AP, a waiting time allowing for 90% of the remaining aerosols to be removed should be adopted before exiting the room. This would limit the risk of aerosols to disperse to the adjacent room when dental providers and the patient are opening the door to leave the room. Then dental personnel should wait an additional period of time before reentering the dental operatory in order to allow for a total of 99.9% of the remaining aerosols to be removed. 2.4 Room Differential Pressure Studies and governmental agencies indicate that directing airflow through a negative pressure isolation room is the preferred model for protecting healthcare providers when performing care to a patient suspected or known to carry an infectious agent, to include patients with COVID-19 [5-8]. Both the United States Centers for Disease Control and Prevention (CDC) and the Academy of Architecture for Health recommend a minimum pressure differential of 0.01 inch water gauge to sustain a negative pressure room [9, 10]. 2.5 Air Changes per Hour CDC recommends a minimum of six ACH as criteria for an efficient ventilation system (12 ACH for new construction or renovation areas) for airborne infection isolation [9]. 2.6 Air Exhaust There are two types of ventilation systems for the control of infection in health-care facilities: single-pass ventilation systems and recirculation systems. In the former, 100% of the supplied air is exhausted to the outside after passing through the room. Therefore, this system is preferred as it prevents contaminated air from being recirculated in other areas of the building. If this cannot be achieved, a recirculation system using air cleaning technologies where air is passed through HEPA filters and/or ultraviolet germicidal irradiation (UVGI) systems before being recirculated to the general ventilation system can be used [5, 11].

8 © Her Majesty the Queen in Right of Canada as represented by the Minister of National Defence. All Rights Reserved. 3 Methodology Though the assessment at NDHQ - Carling Campus Dental Clinic was primarily used as a familiarization with the equipment and to conduct preliminary testing, while the assessment at the other two locations aimed at determining the optimal configuration of air cleaning devices in a clinic dental operatory and in a MDC, the methodology used at all locations shared similarities as described in the following paragraphs. 3.1 Determination of the Optimal Position of the MedEVAC® AP Flange At all three locations assessed, the optimal position of the MedEVAC® AP flange was determined by measuring the capture velocity at the patient’s mouth. The optimal position had to simultaneously allow for adequate visibility and freedom of movement for four-handed dentistry. A smoke tube test was performed to visualize the air flow pattern and to ensure the best positioning of the AP flange.

3.2 Personal and Ambient Air Sampling of PM 10 during Dental Procedures Personal and ambient air sampling was conducted to determine the effectiveness of the selected air cleaning configurations in capturing aerosols. Personal sampling of PM 10 was measured in the breathing zone of x2 dental personnel performing the tasks of a dentist and of a dental assistant during non-aerosol (NAGPs) and aerosol (AGPs) generating procedures. This task was accomplished using laser photometers (SidePak AM510®). PM 10 levels were also measured in the ambient air via two laser photometers (DustTrak DRX™). Both types of photometers, when sampling for PM 10 , have a particle size range of 0.1 µm to 10 µm, and a concentration range of 1 µg/m 3 to 20,000 µg/m 3 (SidePak AM510®) and of 1 µg/m 3 to 150,000 µg/m 3 (DustTrak DRX TM ). However, one significant difference is that the SidePak AM510® measures aerosols with a 50% cut-off size of 10 µm (occupational sampling), while the DustTrak DRX TM measures particles of 10 µm and smaller (environmental sampling). A one-second logging interval was used by all photometers to record PM 10 levels during each test. Testing time was five minutes per condition assessed. At all locations, the background levels of PM 10 were measured first. This measurement was taken by having the air cleaning devices functioning until PM 10 concentrations stabilized (MedEVAC® AP and AF400® AP at Carling and Montfort; MedEVAC® AP and WMAF in the MDC). As the intent was to estimate the efficiency of the MedEVAC® AP, this allowed to know the background levels when the units were functioning. Dental procedures were performed on a full-scale simulated patient with extracted human teeth (none contained restorative materials). The same two dental providers took part in all three assessments. After the familiarization at Carling Campus Dental Clinic, they reversed role which they kept for the remaining assessments. In all cases, the Dentist was right-handed and operated from the 11 o’clock position with the dental chair reclined as normal (patient supine). The AGPs consisted of the Dentist preparing the teeth using a high-speed air-driven hand piece with #557 carbide burs, with the air-water spray coolant turned on as normal. The NAGPs consisted of the Dentist preparing the teeth using a slow-speed electric-driven hand piece with #6 and #8 round carbide burs, with the air-water spray coolant turned off. Burs were changed when dull. In all

9 © Her Majesty the Queen in Right of Canada as represented by the Minister of National Defence. All Rights Reserved. cases, a high-volume evacuation (HVE) suction was used full-time by the Dental Assistant to replicate effective four-handed dentistry. The air-water syringe to clean and dry the teeth and mirror was used as normal procedure during AGPs but not during NAGPs.

3.3 Calculation of the Effectiveness of the MedEVAC® AP in Capturing PM 10

From the recorded PM 10 time-weighted average concentrations, the effectiveness of the APs could be estimated as follows: (PM10 OFF – PM10 ON ) / (PM10 OFF – PM10 Background ) x 100%; using the values obtained with (“ON”) and without (“OFF”) the AP(s) functioning. 3.4 General Ventilation Assessment At all locations, the total supply and/or exhaust airflow was measured using a thermoanemometer (TSI VelociCalc®) or an air capture hood (TSI AccuBalance®). The number of ACH was then calculated. Room differential pressure was measured in the dental operatory at the Montfort Dental Clinic and in the MDC using the TSI VelociCalc®. 3.5 Assessment at NDHQ Carling Dental Clinic Operatory (Positive Pressure Room) At the time of the assessment in the dental operatory of NDHQ Carling Dental Clinic (Figure 1), only an 8-inch conical flange was available for testing on the Medevac® AP extended arm. Besides background PM 10 levels, three conditions were assessed during NAGPs and AGPs for a total of six conditions during which personal and ambient air sampling of PM 10 was performed: - MedEVAC® AP off and AF400® AP off (“both APs off”); - MedEVAC® AP on; and - MedEVAC® AP on and AF400® AP on (“both APs on”). The Dentist conducted NAGPs and AGPs in a manner representing worst-case scenarios that would lead to a maximum of aerosols being generated.

Figure 1. Testing configuration in the dental operatory at the NDHQ Carling Dental Clinic.

10 © Her Majesty the Queen in Right of Canada as represented by the Minister of National Defence. All Rights Reserved. 3.6 Assessment at Montfort Dental Clinic Operatory (Neutral Pressure Room) In the dental operatory of the Montfort Dental Clinic (Figure 2), different flanges provided by the manufacturer of the MedEVAC® AP were tested. The capture velocity provided by these flanges was measured to determine the most effective one. The conditions assessed at NDHQ Carling Dental Clinic were then repeated with that flange only (inverted 8-inch flange) as this configuration presented the highest capture velocity. This time, in addition to NAGPs and AGPs representing worst-case scenarios, dental personnel also performed procedures representative of common operations, for a total of 12 assessed conditions.

Figure 2 . Testing configuration in the dental operatory at the Montfort Dental Clinic. The procedures were also standardized in order to limit differences in aerosol generation from one condition to another. Each 5-minute worst-case scenario was conducted by dental personnel as follows (Q = a quadrant of teeth; Q1 = upper right, Q2 = upper left, Q3 = lower left, Q4 = lower right):

- 1-minute Q1 posterior occlusal preparation; - 1-minute Q2 posterior occlusal preparation; - 1-minute Q3 posterior occlusal preparation; - 1-minute Q4 posterior occlusal preparation; and - 1-minute maxillary (upper) incisor endodontic access preparation.

During representative scenarios, the Dentist prepared a posterior endodontic access cavity (the start of a root canal, one of the common urgent dental treatments) on a mandibular (lower) tooth, starting with an untouched tooth (Picture 3). In these scenarios, measurement of PM 10 lasted five minutes during AGPs, and 10 minutes during NAGPs.

Picture 3. Representative NAGP (A) and AGP (B); worst-case scenario NAGP (C) and AGP (D). 3.7 Assessment in a Mobile Dental Clinic (Negative Pressure Room) In the MDC operatory at CFB Uplands (Figure 3) operations were limited to AGPs under a worst-case scenario and lasted five minutes for all tests. The optimal orientation of the MedEVAC® AP flange determined previously (inverted 8”) was also utilized for all tests.

Figure 3. Testing configuration in the MDC dental operatory at CFB Uplands.

12 © Her Majesty the Queen in Right of Canada as represented by the Minister of National Defence. All Rights Reserved. In addition to the measurement of PM 10 background levels at the MDC, aerosols generated were sampled for each condition listed in Table 4. Table 4. Assessed Conditions at the MDC.

Condition ‰ 1 2 3 4 5 6 7 8 “All ON” “All OFF” MedEVAC® AP ON - ON ON ON - ON - XPOWER X- 2580® Air ON ON - - ON ON - - Scrubber (AS) Wall-Mounted Air Filter ON ON - ON - - - - (WMAF) - HVAC Small Wall- Mounted Air - - - - ON ON - - Filter (SWMAF) - HVAC AF-400® AP ------ON -

4 Results 4.1 Air Changes per Hour and Differential Pressures ACH, total supply and exhaust airflow, room volumes and differential pressures are indicated in Table 5. Each location where testing was conducted had a different room pressure. While the room pressure in the operatory room at NDHQ Carling was found to be positive with an ACH of 27, the room pressure in the operatory at the Montfort Dental Clinic had an ACH of 6 and was neutral, even though there was a significant difference between total supply airflow and total exhaust airflow. No differential pressure with the adjacent corridor could be detected, and a smoke tube test showed little to no movement of particles at the door gap. This may indicate that the room’s leakage area comprises significantly more than just the door gap. The MDC was under negative pressure and had an ACH of 13. Because the MDC had entry ports at the front and at the rear of the room, it was possible to measure differential pressure at both places. A higher negative static pressure was detected at the rear of the MDC, understandably because the AS/exhaust was located there. This indicates the overall movement of air from the front to the rear of the MDC.

13 © Her Majesty the Queen in Right of Canada as represented by the Minister of National Defence. All Rights Reserved. Table 5. Measured Supply and Exhaust Airflows (Cubic Feet per Minute; CFM). Calculated Air Change per Hour (ACH), and Differential Pressure. Total Total Room Room Differential Supply Exhaust Volume Room Pressure ACH Pressure Airflow Airflow (Cubic (+ or -) (inch wc) (CFM) (CFM) Feet)

Positive Operatory – NDHQ pressure room 930 185 + 2,030 27 Carling Dental Clinic confirmed with smoke tube Operatory – Montfort Dental 146 179 Neutral 1,866 6 0.000 Clinic Mobile Dental Clinic No -0.250 (rear) – CFB Uplands (with supply/natural 313 - 1,400 13 -0.045 (front) AS functioning) air

4.2 NDHQ Carling Dental Clinic Operatory (Positive Pressure Room) The initial optimal configuration of the MedEVAC® AP with the 8-inch conical flange providing maximum capture velocity, while allowing for adequate visibility and freedom of movement for four-handed dentistry, was found to be when the bottom part of the flange was at 3 inches above the patient’s chin, and the top part at 6¼ inches from the patient’s nose (Picture 4). However, in that configuration, the measured average capture velocity was only 36 fpm, which is below the recommended 100 fpm guideline. Nonetheless, the MedEVAC® AP was found to collect the majority if not all the aerosols produced by the Gastek® smoke tube when placed at the patient’s mouth.

Picture 4. Initial optimal configuration of the MedEVAC® with the 8” flange (A) and capture of aerosols generated from smoke tubes (B). Using the above flange configuration, results from personal sampling conducted on the Dentist during NAGPs and AGPs indicate an increase of exposure to PM 10 when both APs were not

14 © Her Majesty the Queen in Right of Canada as represented by the Minister of National Defence. All Rights Reserved. operating (Figure 4). AGPs led to a higher exposure of the Dentist to PM 10 than NAGPs, which were both decreased by the use of the MedEVAC® AP. Reducing the PM 10 levels to background concentrations only required the use of the MedEVAC® AP for NAGPs. However, both APs were needed to reduce the particulate concentrations down to background levels for the AGPs.

Figure 4. Personal sampling of PM 10 on the Dentist during NAGPs and AGPs at the NDHQ Carling Dental Clinic. Similar to the results obtained for the Dentist, results from personal sampling conducted on the Dental Assistant during NAGPs and AGPs indicate an increase of exposure to PM 10 when both APs were not operating (Figure 5). These PM 10 levels were decreased when both APs were operating. An increase of exposure to PM 10 was observed when only the MedEVAC® AP was operating during AGPs. This may have been caused by differences in aerosols generated from one condition to the other. Also, it was observed that while the Dentist was often positioned opposite to the direction of the aerosols, the Dental Assistant was often located in the trajectory of the particles produced. Furthermore, the HVE was occasionally withdrawn from the operating field to visualize the difference it made in the generation of spray and capture of this spray by the MedEVAC® AP. These results demonstrated the need for standardizing the assessed dental procedures for consistency in aerosol generation.

Figure 5. Personal sampling of PM 10 on the Dental Assistant during NAGPs and AGPs at the NDHQ Carling Dental Clinic.

15 © Her Majesty the Queen in Right of Canada as represented by the Minister of National Defence. All Rights Reserved. Ambient air sampling indicates a decrease in PM 10 levels when the MedEVAC® AP is operating during dental procedures, with or without the AF400 AP, with concentrations remaining above background levels during AGPs (Figure 6).

Figure 6. Ambient air sampling of PM 10 during NAGPs and AGPs at the NDHQ Carling Dental Clinic. 4.3 Montfort Dental Clinic Operatory (Neutral Pressure Room) All assessed MedEVAC® AP flanges, once their optimal configuration determined as previously explained, allowed for the collection of the majority if not all the aerosols produced by the Gastek® smoke tube when placed at the patient’s mouth (Pictures 5 to 7). The 8” flange however, captured smoke from a larger area around the mannequin’s mouth and when inverted provided the highest capture velocity achievable.

Picture 5. Optimal configuration of the MedEVAC® with the 4-inch circular flange (A) and capture of aerosols generated from smoke tubes (B).

Picture 6. Optimal configuration of the MedEVAC® with the 4” x 6” rectangular flange (A) and capture of aerosols generated from smoke tubes (B).

Picture 7. Optimal configuration of the MedEVAC® with the inverted 8-inch flange (A) and capture of aerosols generated from smoke tubes (B). All assessed flanges, in their optimal configuration, led to a capture velocity near the simulated patient’s teeth below the recommended guideline of 100 fpm (Table 6). According to the manufacturer, increasing the airflow provided by the MedEVAC® AP is not readily achievable without replacing the existing motor with a more powerful one. Table 6 . Recorded Capture Velocities for Optimal Configurations of the MedEVAC®. Flange Capture velocity Distance from the Distance from the (fpm) nose (inches) chin (inches) 8” flange 36 6¼ 3 4” flange 26 6¼ 3 4”x6” flange 33 6 3 Inverted 8” flange 47 7¼ ½

17 © Her Majesty the Queen in Right of Canada as represented by the Minister of National Defence. All Rights Reserved. As the inverted 8” flange led to the highest capture velocity possible, personal and ambient air sampling with this flange configuration was performed at the Montfort Dental Clinic on 22 April 2020. Personal sampling on the Dentist performing a representative scenario of NAGPs and AGPs (Figure 7) showed that having both APs functioning, and to a lesser extent the MedEVAC® AP alone, decreased on average the level of PM 10 that this dental provider is exposed to.

Figure 7. Personal sampling of PM 10 on the Dentist during representative scenarios of NAGPs and AGPs at the Montfort Dental Clinic. The same observations can be made for the Dentist performing worst-case scenarios of NAGPs and AGPs (Figure 8). As part of the worst-case scenarios of AGPs, an additional condition was assessed: flexible ducting connected the outlet of the AF400® AP to the only general ventilation exhaust of the room (Picture 8). This condition was assessed as a possible option to prevent generated bioaerosols from entering the building ventilation system. However, this configuration led to an increase of PM 10 exposure for the Dentist as shown on Figure 8. Furthermore, as confirmed by a smoke tube test, this did not convert the neutral pressure room to a negative pressure room.

Figure 8. Personal sampling of PM 10 on the Dentist during worst-case scenarios of NAGPs and AGPs at the Montfort Dental Clinic.

Picture 8. Flexible ducting connecting the AF400® AP to the general ventilation exhaust. The remaining exhaust area was blocked with clear tape.

Similar to the results obtained for the Dentist, personal sampling on the Dental Assistant performing a representative scenario of NAGPs and AGPs (Figure 9) showed that having both APs, and to a lesser extent the MedEVAC® AP alone, decreased on average the level of PM 10 that this dental provider is exposed to.

Figure 9. Personal sampling of PM 10 on the Dental Assistant during representative scenarios of NAGPs and AGPs at the Montfort Dental Clinic. The same observations can be made for the Dental Assistant performing worst-case scenarios of NAGPs and AGPs (Figures 10). However, exposure of the Dental Assistant to PM 10 is not as high as observed for the Dentist when the AF400® AP is connected to the general ventilation exhaust. It can nonetheless be noted that once the AF400 was connected to the general ventilation exhaust, it took much longer for the PM10 measurements to return to background levels. After 15 minutes, the PM 10 generated by the previous condition still had not returned to background levels and the AF400® AP was disconnected from the general ventilation exhaust to proceed with the next condition.

Figure 10. Personal sampling of PM 10 on the Dental Assistant during worst-case scenarios of NAGPs and AGPs at the Montfort Dental Clinic.

For all assessed conditions, the lowest PM 10 levels in ambient air were recorded when both APs were in operation (Figures 11 and 12). Also, returning ambient air PM 10 concentration to background levels by reactivating the MedEVAC® AP and AF400® AP after a worst-case scenario of AGP without any AP functioning took approximately 7.5 minutes.

Figure 11. Ambient air sampling of PM 10 during NAGPs and AGPs. Representative scenario. MedEVAC® AP with inverted 8-inch flange.

Figure 12. Ambient air sampling of PM 10 during NAGPs and AGPs. Worst-case scenario. MedEVAC® AP with inverted 8-inch flange.

21 © Her Majesty the Queen in Right of Canada as represented by the Minister of National Defence. All Rights Reserved. Time weighted averages (20 sec.) concentrations obtained from personal sampling of PM 10 aerosols for the dentist and dental assistant under various equipment configurations are presented in Annex A, in comparison to background levels and to the “Both APs ON” and “Both APs OFF” conditions. 4.4 Mobile Dental Clinic at CFB Uplands (Negative Pressure Room)

Results from personal sampling conducted on the Dentist showed that the highest PM 10 time- weighted average (5 min) concentration was obtained with the WMAF and AS in operation, while the lowest concentration was achieved with the WMAF functioning with the MedEVAC® AP (Figure 13). The concentration recorded when the WMAF and the AS were in operation was even higher than when there was no air filtration unit functioning. The four conditions with the AS functioning are among the highest concentrations recorded.

Dentist exposure to PM 10 when the SWMAF and AS were functioning was above background but lower than the “All OFF” condition; with the addition of the MedEVAC® AP, exposure was reduced by a factor of two. When only the MedEVAC® AP was functioning, with or without the AF-400® AP, dentist exposure to aerosols was reduced to background levels.

Figure 13. Dentist’s exposure to PM 10 during worst-case scenarios of AGPs in the MDC at CFB Uplands for different equipment configurations.

As for the results obtained for the Dentist, the Dental Assistant’s exposures to PM 10 in all assessed configurations that included the MedEVAC® AP were at or below that of the “All ON” condition and were similar to background levels (Figure 14). Configurations without the MedEVAC® AP were similar to or exceeded the “All OFF” condition.

Figure 14. Dental Assistant’s exposure to PM 10 during worst-case scenarios of AGPs in the MDC at CFB Uplands for different equipment configurations.

Ambient air concentrations of PM 10 aerosols were equivalent to background levels under the “All ON” condition; they were slightly above background levels under the “All OFF” condition. Except for the “All ON” condition, all configurations with the AS functioning led to an ambient air concentration of PM 10 above the one recorded under the “All OFF” condition. Ambient air concentrations of PM 10 were lowest when the MedEVAC® AP was functioning, with or without the WMAF (Figure 15).

Figure 15. Comparison of equipment configurations for PM 10 ambient air sampling during AGPs, worst-case scenario.

23 © Her Majesty the Queen in Right of Canada as represented by the Minister of National Defence. All Rights Reserved. Time-weighted average (20 sec.) concentrations obtained for the dentist from personal sampling under various equipment configurations are presented in Annex B, in comparison to background levels and to the “All ON” and “All OFF” conditions. Logged per-second data could not be extracted for the dental assistant due to technical issues; data recovery by the manufacturer was unsuccessful. Nonetheless, minimum, maximum, and average values were available for all tested conditions.

The 20-second time-weighted average graphs B1 to B6 show that the PM 10 readings were consistently higher in the second, third, and fifth minutes of each condition assessed (particularly in the “All OFF” condition), which represents the times when the Dentist was operating on the upper left, lower left, and upper anterior teeth, respectively. 4.5 Estimated Effectiveness of the MedEVAC® AP under Various Conditions

From the PM 10 concentrations measured through personal sampling, the estimated effectiveness of the MedEVAC® AP in capturing PM 10 as assessed for the various conditions is shown in Table 7, for the conditions assessed at the NDHQ Carling and Montfort Dental Clinics, and in Table 8, for the conditions assessed in the MDC at CFB Uplands. In all conditions assessed with the 8-inch inverted flange, when both APs were functioning, an effectiveness of 100% was achieved at the Montfort Dental Clinic (Table 7). Such results were not obtained from the assessment conducted with the straight 8” flange at NDHQ Carling Dental Clinic. This may be explained by the lowest capture velocity provided under this flange configuration as well as by a lack of standardization of the dental procedures conducted for this first assessment. Table 7. Estimated Effectiveness (%) of the MedEVAC® and AF400® APs in Reducing Exposure to PM 10 Generated during Dental Procedures. Flange: 8” flange Inverted 8” flange (testing location) (Carling) (Montfort) Scenario: Worst-case Worst-case Representative Personnel → Dental Dental Dental Dentist Dentist Dentist Condition ↓ Assistant Assistant Assistant MedEVAC 100 83 100 100 100 100 on NAGPs Both APs 100 83 100 100 100 100 on MedEVAC 41 0 53 88 50 100 on AGPs Both APs 100 73 100 100 100 100 on AGP Both APs on with 0 100 AF400 to Exhaust

24 © Her Majesty the Queen in Right of Canada as represented by the Minister of National Defence. All Rights Reserved. In the MDC, in all conditions where the MedEVAC was used without the AS, an effectiveness of 100% was achieved (Table 8). Table 8. Estimated Effectiveness (%) of the MedEVAC and AF400 APs in Limiting Exposure to PM 10 Generated during Dental Procedures in the MDC. Condition Dentist Dental Assistant MedEVAC-WMAF 100 100 MedEVAC-AF400 100 100 MedEVAC 100 100 All ON 89 100 SWMAF-MedEVAC-AS 89 100 SWMAF-AS 56 0 WMAF-AS 0 0

Though an effectiveness of 100% at capturing PM 10 was calculated for specific conditions, in all cases, larger visible droplets and aerosols were produced, often landing on the surrounding environment, uncaptured by the MedEVAC® AP. A fair portion of these debris also landed on the flange of the MedEVAC® AP (Picture 9).

Picture 9. The MedEVAC® AP flange showing deposition of larger debris after dental procedures.

5 Discussion As mentioned previously, because of the interrelation of air cleaning devices and general ventilation systems on air quality, parameters affecting both engineering controls will be covered in the following discussion.

25 © Her Majesty the Queen in Right of Canada as represented by the Minister of National Defence. All Rights Reserved. 5.1 Room Differential Pressures As previously mentioned, a negative pressure room is preferred for the control of infection transmission in healthcare settings, to include COVID-19 [5-8]. All three assessed locations had different room pressures compared to the adjacent environment: positive (NDHQ Carling Dental Clinic), neutral (Montfort Dental Clinic) or negative (MDC). At the NDHQ Carling Dental Clinic, achieving a negative pressure at the assessed dental operatory would most likely be difficult given the large difference between supply and exhaust airflows. As such, using a different room where a negative pressure could be more easily achievable would be preferable. An alternative would be to rebalance the general ventilation system to achieve negative pressure in the dental operatory. This option however may involve substantial modifications to the current system. A third option is to use the XPOWER X-2580® AS (which is deemed unnecessary for the MDC as discussed further) to exhaust the air to an adjacent room through a wall or door. The existing metal door could be replaced with a temporary wooden door which would allow connecting the XPOWER X-2580’s exhaust. In all cases, the effectiveness of the MedEVAC® AP would have to be reassessed. Though connecting the AF400® AP to the exhaust vent of the dental operatory at the Montfort Dental Clinic could prevent the dissemination of aerosols generated by dental procedures to the general ventilation system of the building, this led to an increase of PM 10 exposure for the Dentist. This may be explained by the fact that the additive effect on aerosol clearance in the room by both the general ventilation exhaust and the AF400® is lost by connecting the systems together. Furthermore, this configuration did not allow the neutral differential pressure in the room to become negative. As room pressure was neutral, it may be possible to rebalance the general ventilation system to achieve a negative pressure room in the dental operatory. If not, the other two options mentioned above (change room or use of the AS) are also applicable to this room.

Although a negative pressure was easily achieved in the MDC, results from PM 10 sampling indicate a decrease in the efficiency of the MedEVAC® AP. The creation of a relatively high negative pressure in such a small room through the use of the AS (at a power level of 5 out of 5) may create air turbulence and cross drafts that decrease the efficiency of the MedEVAC® AP to capture aerosols generated by dental procedures. Miller-Leiden et al. (1996) explain that both the air flow configuration of the APs and their placement within the room are important, influencing room air flow patterns and the spatial distribution of concentrations. Also, as seen in Figure 3, the dental chair was angled compared to the air flow generated by the pressure gradient in the MDC (from the front of the MDC to the back). Air drafts crossing the front section of the MedEVAC® AP flange could prevent particles from being effectively captured by the AP. Consequently, and since MDCs are single rooms giving directly to the outdoor, achieving a negative pressure room to protect personnel in adjacent rooms is not necessary.

26 © Her Majesty the Queen in Right of Canada as represented by the Minister of National Defence. All Rights Reserved. 5.2 Air Exhaust As mentioned previously, to control infection transmission in healthcare settings, if exhausted air cannot be directly funneled to the outside of the building, the air should first pass through a HEPA filter and/or UVGI system before recirculation [5, 11]. This recommendation is consistent with the fact that aerosols produced in dentistry have the ability to remain airborne for an extended period of time [12]. This explains the observed increase of PM 10 in ambient air during dental procedures as measured by the DustTrak® photometers. Consequently, there is a potential for these aerosols to enter the ventilation system and spread to areas of the facility where barrier protection is not used [3]. Though this has yet to be scientifically proven for the aerosol transmission of SARS-CoV-2, precautionary measures should be taken [13]. In this regard, safe air exhausting is certainly not an issue for the MDCs. However, in the dental operatories of NDHQ Carling Dental Clinic and Montfort Dental Clinic, if the exhaust air cannot be directly funneled to the outside, and if a HEPA filter cannot be installed on exhaust vents, then directing the airflow of the AP filtering ambient air towards the exhaust vent could limit the spread of the generated aerosols towards the general ventilation system. In addition, if an AS is used to create a negative pressure room at both locations, this would further limit aerosols from reaching the exhaust of the general ventilation system. Such alternative is however far less desirable than the first two options. 5.3 Effectiveness of the Assessed Air Cleaning Devices At both the NDHQ Carling and Montfort Dental Clinics, during NAGPs and AGPs, the MedEVAC® AP decreased PM 10 concentrations to background levels in many cases, and a further decrease was observed when used in combination with the AF400® AP. This observation was made from both personal sampling and ambient air sampling. This shows that capturing a contaminant at the source not only limits exposure of dental providers to aerosols, but also limits these aerosols from diffusing in ambient air and from dispersing in the general ventilation system. This is consistent with studies that showed the effectiveness of APs in controlling aerosol dispersion emitted from a patient’s mouth in dental clinics [6, 14-16]. The use of the AF400® AP in the dental operatory rooms (NDHQ Carling and Montfort) not only decreased PM 10 concentrations in the ambient air, but also decreased the exposure of dental providers to the generated aerosols during the procedures as shown by the results from personal sampling. This observation demonstrates the ability of aerosols produced in dentistry to remain airborne [12].

Consequently, an effectiveness of 100% of the MedEVAC® AP in capturing PM 10 in the breathing zones of both dental providers was achieved for all conditions assessed with the inverted 8-inch flange at the Montfort Dental Clinic when the AF400® AP was functioning. Such effectiveness was achieved in the MDC for any condition when the MedEVAC® AP was functioning without the use of the AS. The combination of the WMAF with the MedEVAC® AP

27 © Her Majesty the Queen in Right of Canada as represented by the Minister of National Defence. All Rights Reserved. led to the lowest PM 10 concentrations recorded from personal sampling and ambient air sampling. These results demonstrate that combining the filtration capacity of an air cleaning device capturing aerosols at the source and of another filtering ambient air leads to the lowest PM 10 concentrations possible with the various air cleaning devices assessed. This is consistent with a former study demonstrating that the key to aerosol control is to capture droplet nuclei in high concentrations near the source before they disperse throughout the room [16]. The same study also explains that an additional ambient air filtration unit offers supplementary protection by capturing dispersed droplet nuclei. 5.4 Dental Procedures and Peak Concentrations of Generated Aerosols

Many of the highest 20-second time-weighted averages of PM 10 concentrations from personal sampling were observed in the last minute of the five-minute worst-case scenarios (Figures A8 and B1 to B8). This may be explained by the fact that a maxillary incisor endodontic access preparation was conducted during this last minute, while posterior occlusal preparations were performed for the first four minutes. The location of the procedure (upper anterior teeth) could lead to more aerosols being directed towards dental providers, in particular the dentist. This increase of PM 10 was mostly observed when all APs were not functioning, which supports the effectiveness of the tested air purifying system (without the AS functioning in the case of the MDC). The second highest concentrations recorded by personal sampling during worst-case scenarios were mainly found between 60 and 180 seconds (Figures A3, A4 and B1 to B6), which represents the times when the Dentist was operating on the upper left and lower left quadrants. At these locations, the dentist's operating hand (right) may have led to aerosols being directed towards both dental providers. This increase was mostly observed in conditions when the MedEVAC® AP was not functioning. However, in some cases (Figures A7 and B6), this increase was also seen in conditions when the MedEVAC® AP was functioning, suggesting that the dentist’s hand may have partially been blocking the capture velocity provided by the AP. 5.5 Air Cleaning Device Limitations and Appropriate Controls Though the majority (90%) of aerosols produced in dental settings are smaller than 5 µm, the larger generated aerosols (droplets ( ≤ 50 µm) and spatter (>50 µm)) nonetheless represent a significant volume. As such, though an effectiveness of 100% in capturing PM 10 was calculated for the MedEVAC® AP for many assessed conditions, larger uncaptured aerosols were contaminating the surrounding surfaces. This reinforces the need, even when the MedEVAC® AP is used during dental procedures, for the proper donning of personal protective equipment and the implementation of efficient administrative controls as recommended by governmental agencies and the scientific literature [5, 8, 17-21]. Also, though the initial background PM 10 level was used as a surrogate indicating the complete clearance of aerosols generated during dental procedures, it is understood that such PM 10 level would most likely contain a proportion of aerosols generated during the dental procedures.

28 © Her Majesty the Queen in Right of Canada as represented by the Minister of National Defence. All Rights Reserved. 5.6 Waiting Periods before Exiting and Reentering Clinic Dental Operatories and MDCs As mentioned earlier, before exiting the dental operatory after a procedure requiring the use of the MedEVAC® AP, the dental providers and the patient would have to wait in order to allow for the removal of 90% of the remaining aerosols. Before reentering the dental operatory, personnel would have to wait for the removal of 99.9% of the remaining aerosols. The time required to achieve these removal efficiencies is based on the ACH specific to each room. As Table 5 showed, the number of ACH provided by the general ventilation system can vary greatly from one dental operatory to another. As such, a conservative approach would be to only take into consideration the air filtered by the air cleaning devices to account for aerosol removal.

Considering the relatively short time (7.5 minutes) it took for PM 10 concentrations to be reduced to background levels after a dental procedure when APs were functioning, the MedEVAC® AP, the AF400® and the WMAF (MDC) would play an active role in aerosol clearance during and after the completion of such procedures. Consequently, in a dental operatory of 2,000 ft 3 (a value close to the volumes of the dental operatories assessed), the combined filtration airflow provided by the MedEVAC® AP and the AF400® AP (450 CFM) would allow for 14 ACH (rounded up). Looking at Table 3, a waiting period of 10 minutes is needed before exiting the room, and an additional 20 minutes before reentering the room, for a total of 30 minutes. With a volume of 1,400 ft 3 and a combined filtration airflow of 1230 CFM, the WMAF and the MedEVAC® AP would provide 53 ACH in the MDC. As demonstrated by the calculations presented in Annex C, this corresponds to a waiting time of 3 minutes before exiting the MDC after a dental procedure requiring the use of the MedEVAC® AP, and an additional 5 minutes before reentering the MDC. 5.7 Limitations Statistical significance was not expected in this assessment given that only two dental providers where available and the high number of conditions to assess for the resources and time available. The resolution of both types of photometers was 1 µg/m 3. As such, to consider two results different, with an absolute error of +/- 1 µg/m 3, a difference of 2 µg/m 3 should be observed. 3 Several differences in PM 10 concentrations between conditions were less than 2 µg/m . The main reason for such a low difference is the fact that the measured concentrations were relatively low, close to the detection limit of the photometers. An analysis of variance (ANOVA; pairwise comparisons) was conducted on SPSS® by pooling the data obtained from both the Dentist and the Dental Assistant and doing the same with the results from both environmental photometers. The differences observed between all conditions and the “All OFF” condition for each assessment were not statistically significant (alpha = 0.05). This can be attributed to the low number of iterations (2) per condition tested, besides the low concentrations recorded as mentioned above.

29 © Her Majesty the Queen in Right of Canada as represented by the Minister of National Defence. All Rights Reserved. Though statistical significance was not achieved, the consistency of the results from one condition to another in the various real-life scenarios assessed supports the conclusions of this report.

6 Conclusions The use of the MedEVAC® AP had the greatest impact on reducing exposure of dental personnel to aerosols generated during NAGPs and AGPs, regardless of the type of dental operatory and room pressure, often bringing PM 10 concentrations to background levels. In dental operatory rooms (Carling and Montfort), when the MedEVAC® AP was used in combination with the AF400® AP during NAGPs and AGPs, the airborne particulate concentrations were reduced even further, often falling below background levels, leading to an estimated effectiveness of 100% at capturing PM 10 .

In the MDC, the use of the WMAF with the MedEVAC® led to a higher reduction of PM 10 concentrations than the MedEVAC® used with or without the SWMAF, with concentrations falling below background levels and corresponding to an estimated effectiveness of 100% in capturing PM 10 . Thus, it is expected that the combination of the MedEVAC® AP with the AF400® AP or with the WMAF would significantly decrease the risk of dental providers to be exposed to SARS- CoV-2 while performing dental procedures.

In the MDC, the use of the AF-400® AP with the MedEVAC® AP did not reduce PM 10 concentrations compared to the use of the MedEVAC® only.

In most assessed conditions in the MDC, the use of the AS increased exposure to PM 10 during AGPs. This observation, in addition to the fact that the MDC’s adjacent environment is the outdoor, demonstrates that achieving a close to neutral pressure room at that particular location is preferable to a negative pressure room. Connecting the AF400® AP to the room’s exhaust diffuser at the Montfort Dental Clinic increased exposure to PM 10 in the dental operatory and did not allow to achieve a negative pressure room. In all assessed rooms after dental procedures, a maximum of approximately 7.5 minutes was sufficient for the combination of APs (MedEVAC® AP with AF400® AP or with WMAF) to decrease PM 10 concentrations to background levels. The presence of uncaptured droplets and spatter on the surrounding environment indicates the need to complement the use of the MedEVAC® AP with proper administrative controls and personal protective equipment, as recommended by governmental agencies and the scientific community for preventing the transmission of infection in healthcare settings.

30 © Her Majesty the Queen in Right of Canada as represented by the Minister of National Defence. All Rights Reserved. 7 Recommendations This assessment took place in closed dental operatory rooms and as such the conclusions and recommendations of this report do not apply to open room settings. To limit the risk of exposure to SARS-CoV-2 by dental providers, the MedEVAC® AP and the AF400® AP should be used during and after procedures performed in closed dental operatory rooms (e.g. NDHQ Carling and Montfort Dental Clinics).

The MedEVAC® AP and the WMAF should be used during and after procedures performed in the MDC.

After each dental procedure requiring the use of the MedEVAC®/AF400® APs in clinic dental operatories or MedEVAC® AP/WMAF in a MDC, both air cleaning devices should be kept functioning for a least 10 minutes (clinic dental operatories) or 3 minutes (MDCs) before personnel exit the room, based on the number of ACH provided by the air cleaning devices and PHAC guidelines. At this point, 90% removal efficiency of the remaining aerosols will have been achieved. Dental personnel should wait an additional 20 minutes (clinic dental operatories) or 5 minutes (MDCs) before reentering the room. At this point, 99.9% removal efficiency of the remaining aerosols will have been achieved. Clinic dental operatory rooms should be kept under slight negative pressure to prevent airborne particulates from migrating outside the rooms. This may entail investigating potential air leakage above the dropped ceiling in the dental operatory of the Montfort Dental Clinic, the rebalancing of the general ventilation systems, the selection of a more appropriate room, or the use of the XPOWER X-2580® AS. The XPOWER X-2580® AS in the MDC to create a negative pressure should not be used when using the MedEVAC® AP. Where feasible, aerosols produced during dental procedures should be prevented from entering the general ventilation system. This can be accomplished by having the exhaust directly funneled to the outside or by installing a HEPA filter on the exhaust vent(s). Alternatively, directing the airflow of the AP filtering ambient air towards the exhaust vent could limit the spread of the generated aerosols towards the general ventilation system. Standard operating procedures (SOPs) should be written to ensure appropriate usage of the APs, to include the configuration of the MedEVAC® AP flange and the use of ambient air purifiers/air filters (AF400® AP and WMAF). These SOPs should also provide guidance on the proper personal protective equipment to wear as well as supporting administrative controls as recommended by governmental agencies and the scientific community [5, 8, 17-21].

31 © Her Majesty the Queen in Right of Canada as represented by the Minister of National Defence. All Rights Reserved. 8 References 1. James, R., and Mani, A., Dental Aerosols: A Silent Hazard in Dentistry! International Journal of Science and Research, 2016. 5(11). 2. Baumann, K., Boyce, M., and Catapano-Martinez, D., Dental Aerosols: The Infection Connection. Dimensions of Dental Hygiene, 2018. 16(10). 3. Harrel, S.K. and J. Molinari, Aerosols and splatter in dentistry: a brief review of the literature and infection control implications. J Am Dent Assoc, 2004. 135(4): p. 429-37. 4. American Conference of Governmental Industrial Hygienists, Industrial Ventilation: A Manual of Recommended Practice for Design . 28 ed. 2013. 5. Public Health Agency of Canada, Routine Practices and Additional Precautions for Preventing the Transmission of Infection in Healthcare Settings . 2013. 6. Chen, C., et al., The effectiveness of an air cleaner in controlling droplet/aerosol particle dispersion emitted from a patient's mouth in the indoor environment of dental clinics. Journal of the Royal Society, Interface, 2010. 7(48): p. 1105-1118. 7. Cheong, K.W.D. and S.Y. Phua, Development of ventilation design strategy for effective removal of pollutant in the isolation room of a hospital. Building and Environment, 2006. 41(9): p. 1161-1170. 8. U.S. Centers for Disease Control and Prevention. Interim Infection Prevention and Control Guidance for Dental Settings During the COVID-19 Response . Available from: https:// www.cdc.gov/coronavirus/2019-ncov/hcp/dental-settings.html . 9. U.S. Centers for Disease Control and Prevention. Guidelines for Environmental Infection Control in Health-Care Facilities . 2003; Available from: https:// www.cdc.gov/infectioncontrol/guidelines/environmental/background/air.html . 10. Academy of Architecture for Health. Guidelines for Design and Construction of Health Care Facilities . 2006; Available from: https:// www.fgiguidelines.org/wp- content/uploads/2016/07/2006guidelines.pdf . 11. Lee, J.Y., Tuberculosis Infection Control in Health-Care Facilities: Environmental Control and Personal Protection. Tuberculosis and respiratory diseases, 2016. 79(4): p. 234-240. 12. Williams and Wilkins, Practical Infection Control in Dentistry . 2nd ed. 1996, Baltimore, Md. 13. Ge, Z.-y., et al., Possible aerosol transmission of COVID-19 and special precautions in dentistry. Journal of Zhejiang University. Science. B, 2020: p. 1-8. 14. Marier, R.L. and T. Nelson, A ventilation-filtration unit for respiratory isolation. Infect Control Hosp Epidemiol, 1993. 14(12): p. 700-5. 15. Rutala, W.A., et al., Efficacy of portable filtration units in reducing aerosolized particles in the size range of Mycobacterium tuberculosis. Infect Control Hosp Epidemiol, 1995. 16(7): p. 391-8. 16. Miller-Leiden, S., et al., Effectiveness of In-Room Air Filtration and Dilution Ventilation for Tuberculosis Infection Control. Journal of the Air & Waste Management Association, 1996. 46(9): p. 869-882. 17. Meng, L., F. Hua, and Z. Bian, Coronavirus Disease 2019 (COVID-19): Emerging and Future Challenges for Dental and Oral Medicine. Journal of dental research, 2020. 99(5): p. 481-487. 18. Peng, X., et al., Transmission routes of 2019-nCoV and controls in dental practice. International journal of oral science, 2020. 12(1): p. 9-9.

32 © Her Majesty the Queen in Right of Canada as represented by the Minister of National Defence. All Rights Reserved. 19. Fallahi, H.R., et al., Being a front-line dentist during the Covid-19 pandemic: a literature review. Maxillofacial plastic and reconstructive surgery, 2020. 42(1): p. 12-12. 20. Fini, M.B., What Dentists Need to Know about COVID-19. Oral Oncology, 2020: p. 104741. 21. Public Health Agency of Canada, Infection Prevention and Control for COVID-19: Second Interim Guidance for Acute Healthcare Settings . 2020.

Individual comparison of conditions assessed during PM 10 personal sampling conducted on dental providers at the dental operatory of the Montfort Dental Clinic with the “Both On” and “Both Off” conditions (20 sec. time-weighted averages)

Figure A1. Personal sampling of PM 10 on the Dentist during NAGPs. Representative scenario. MedEVAC® AP with inverted 8-inch flange.

Figure A2. Personal sampling of PM 10 on the Dentist during AGPs. Representative scenario. MedEVAC® AP with inverted 8-inch flange.

Figure A3. Personal sampling of PM 10 on the Dentist during NAGPs. Worst-case scenario. MedEVAC® AP with inverted 8-inch flange.

Figure A4. Personal sampling of PM 10 on the Dentist during AGPs. Worst-case scenario. MedEVAC® AP with inverted 8-inch flange.

Figure A5. Personal sampling of PM 10 on the Dental Assistant during NAGPs. Representative scenario. MedEVAC® AP with inverted 8-inch flange.

Figure A6. Personal sampling of PM 10 on the Dental Assistant during AGPs. Representative scenario. MedEVAC® AP with inverted 8-inch flange.

Figure A7. Personal sampling of PM 10 on the Dental Assistant during NAGPs. Worst-case scenario. MedEVAC® AP with inverted 8-inch flange.

Figure A8. Personal sampling of PM 10 on the Dental Assistant during AGPs. Worst-case scenario. MedEVAC® AP with inverted 8-inch flange.

Individual comparison of conditions assessed during PM 10 personal sampling conducted on the Dentist at the MDC at CFB Uplands with the “Both On” and “Both Off” conditions (20 sec. time-weighted averages)

Figure B1. Personal sampling of PM 10 on the Dentist during AGPs, worst-case scenario, with MedEVAC® AP in operation.

Figure B2. Personal sampling of PM 10 on the Dentist during AGPs, worst-case scenario, with MedEVAC® AP and AF-400® AP in operation.

Figure B3. Personal sampling of PM 10 on the Dentist during AGPs, worst-case scenario, with wall-mounted air filter (WMAF) and air scrubber (AS) in operation.

Figure B4. Personal sampling of PM 10 on the Dentist during AGPs, worst-case scenario, with wall-mounted air filter (WMAF) and MedEVAC® AP in operation.

Figure B5. Personal sampling of PM 10 on the Dentist during AGPs, worst-case scenario, with small wall-mounted air filter (SWMAF) and air scrubber (AS) in operation.

Figure B6. Personal sampling of PM 10 on the Dentist during AGPs, worst-case scenario, with MedEVAC® AP, small wall-mounted air filter (SWMAF), and air scrubber (AS) in operation.

40 © Her Majesty the Queen in Right of Canada as represented by the Minister of National Defence. All Rights Reserved. Appendix C Calculated Duration before Exiting and Reentering the MDC after a Dental Procedure Requiring the Use of the MedEVAC® AP The following calculations are based on: - the aerosol removal efficiency provided by one room air change (AC) as indicated by ACGIH (63%; Bioaerosols Assessment and Control, 1999) and used by PHAC to recommend time required for removal efficiencies of airborne contaminants (Table 3); and - a calculated ACH of 53 in the MDC, as provided by using the MedEVAC® AP and the WMAF. % of removal efficiency = 1 – (0.37 AC ) 90% removal efficiency = 1 – (0.37 AC ) 0.90 = 1 - (0.37AC ) 0.90 - 1 = - (0.37AC ) 0.10 = (0.37AC ) Log 0.10 / Log 0.37 = AC AC = 2.3 (i.e. 2.3 air changes are required to achieve 90% removal efficiency of aerosols) Time for 90% aerosol removal efficiency = (2.3 AC x 60 minutes / hour) / ACH = (2.3 AC x 60 minutes / hour) / 53 ACH = 2.6 minutes ≈ 3 minutes 99.9% removal efficiency = 1 – (0.37AC ) 0.999 = 1 - (0.37AC ) 0.999 - 1 = - (0.37AC ) 0.001 = (0.37AC ) Log 0.001 / Log 0.37 = AC AC = 6.9 (i.e. 6.9 air changes are required to achieve 99.9% removal efficiency of aerosols) Time for 99.9% aerosol removal efficiency = (6.9 AC x 60 minutes / hour) / ACH = (6.9 AC x 60 minutes / hour) / 53 ACH = 7.8 minutes ≈ 8 minutes