Dental practices must take the proper precautions to keep their staff and patients as safe as possible while the COVID-19 pandemic continues. Air scrubbing technology is one such solution — alongside measures like personal protective equipment and social distancing. But dentists are faced with a surfeit of considerations: standalone units; heating, ventilation and air conditioning (HVAC) retrofitting; different features; and different brands. Additionally, many air filtration products lack evidence demonstrating their efficacy in dental settings.¹ 

Air filtration and air flow are important factors in maintaining a safe environment in dental practices, but the best approach for dental offices remains uncertain. As more research is conducted and new protocols emerge, what should a dental practice know when considering the purchase of an air scrubber? 

How the Technology Works

Before making a purchase, it’s important to understand how air filtration works. COVID-19 is transmitted primarily person to person via respiratory droplets.² This is particularly of concern in dental offices because patients’ saliva can be aerosolized during treatment.³ The goal of air scrubbing technology is to reduce the amount of airborne contamination. Virus particles in the air are minuscule, which means air filtration technology must be capable of removing particles as small as 0.1 to 1 micron.⁴ COVID-19 virus particles are approximately 0.125 micron.⁵ Air filtration technology is available in two main categories: 

• HVAC. A dental office’s HVAC system can be equipped with filters designed to purify the air. Some offices likely have this type of system in place already, but how powerful is the filtration? HVAC systems have parameters determining how many cubic feet of air they can pull in a certain amount of time and how dense the air filters can be. If the system is being used to push air through higher density filters than it is designed for, the motor will be overworked, according to Larry N. Williams, DDS, MAGD, ABGD, associate professor at Midwestern University College of Dental Medicine in Downers Grove, Illinois. 
  
  If you are evaluating your current HVAC filtration system, look up its filtration parameters: How many cubic feet of air can it pull per hour, and how powerful are its filters? It is possible to modify existing HVAC systems by installing a bigger motor for the air-return system. Several regulatory agencies, including the Centers for Disease Control and Prevention (CDC), Environmental Protection Agency (EPA), and the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), are recommending that office buildings check that their HVAC systems are properly filtered and upgrade their filters to the highest possible compatible
  efficiency.⁴ 
• Standalone units. Standalone units that plug into electrical outlets are also an option. This type of air filtration can be used in concert with an HVAC filtration system. Dentists can place standalone units strategically throughout their offices. Sami I. Shahhal, DDS, founder of the “Smile Influencers” blog and practicing dentist in southern California, purchased two air purification units for his office and placed each in an operating room. 
  
  Standalone units are designed to provide air filtration based on room size. Williams contributed to the decision to buy air cleaning systems at his university and was responsible for helping to select air filtration units for its offices. “We bought units that were a little bit more powerful,” he said. “Our offices are 100 square feet, so the filtration system is for 200 square feet. That is a little added safety factor.” 
  
  When determining where to place a standalone unit, consider any areas of the office that may have poor ventilation or a high likelihood of airborne contamination, requiring additional air filtration.⁴ 

Specifications to Consider
 
The CDC has released infection prevention guidance for dental practices during the pandemic, which includes the recommendations to upgrade your practice’s HVAC system and to consider the use of air filtration units.⁶ As you shop for your practice’s air filtration technology, what are the most important specifications? 

• HEPA filtration. High efficiency particulate air (HEPA) filters are typically considered the gold standard of air filtration technology, but not all of these filters are created equal.⁷ One study found that H12 class HEPA filters removed 83% of aerosols that may spread COVID-19, while an air purifier with an F6 class filter removed only 54% of aerosols.³ Check the performance of HEPA filters, both those intended for use in the HVAC system and in standalone units. What is the smallest particle size, measured in microns, the filter can capture?
• Clean air delivery rate. Clean air delivery rate (CADR), the cubic feet of air cleaned per minute, is another measure of a filtration system’s performance. A higher CADR translates to faster air filtration performance.⁶ 
• UVC disinfection. If your air purification system touts the use of ultraviolet (UV) radiation to kill germs, consider what type. Some air filtration systems use UVC, which is meant to kill contaminants like COVID-19. Research has shown that UVC radiation can inactivate the virus, but it requires direct exposure at a duration dependent on the dose.⁸ Direct UVC can be harmful to humans, so this technology is often installed in ventilation systems. UVA and UVB are thought to be less effective than UVC at inactivating COVID-19, according to the FDA.⁸ 
• Noise. Dentists’ offices will always have some level of noise during operating hours, and your air filtration system could be a contributing factor. Check the decibel rating on the systems you are considering. For a general benchmark, a noise rating of 50 decibels means the system will make noise equivalent to a refrigerator, according to Consumer Reports.⁹ 
• Maintenance. Maintenance is an ongoing cost associated with air scrubbing technology. How often do the filters need to be changed? How expensive are the filters? You can likely change the filters on the standalone units yourself, but HVAC systems may require professional maintenance. 
• Electricity usage. Dental practices will also need to pay to operate air filtration systems, whether they are using HVAC, standalone units or both. Ask your HVAC professional about energy usage, and do your research on annual operating costs for standalone units. 

Making the Investment
 
Once you decide that a filtration unit should be in your practice, it can be helpful to: 

• Understand your practice’s needs. Before making any purchase, take the time to evaluate your current air filtration and flow. 
  
  “Where does air come from? How is it returned? Do you have fresh air or no fresh air? Is there an exchange rate? In other words, how often is the air in the room changed out?” said Williams. “That is all that keeps the aerosols from taking over the room.” 
  
  That evaluation is best conducted by a professional. “Get an engineer to come in. This should not be guesswork,” said Williams. “Trained engineers can tell you how much air you are exchanging per hour.” Armed with that knowledge, you can better understand what upgrades, if any, need to be made to your HVAC system. 
• Do your research. Shahhal ultimately decided to buy an IQAir HealthPro Plus filtration system for his office after doing careful online research. “Talk to a community of dentists who have the system,” said Shahhal. “There is a lot of information out there to help dentists make educated decisions. I used the power of forums and sharing information online to make a purchasing decision.” 
  
  As dentists consider their options, beware of how companies market their products. Some options available may be more gimmick than effective solution. “They may be promising a lot, but the research just isn’t there. I am not saying it won’t be in the future, but it is not there right now,” said Williams. 
• Remember the importance of proper maintenance. Once you’ve made your purchase and had your HVAC system upgraded and standalone units installed, commit to a regular maintenance schedule. A poorly maintained system will not be nearly as effective. “Make sure you have a supply of filters on hand, and change them when necessary,” said Williams. “If you want to burn a system up fast, run it with a dirty filter for a while, and watch what happens to your motor.” 
• Talk about your investment. Some patients remain anxious about coming into the office for dental care during the pandemic. If they ask what safety precautions have been taken, talk about the investment in air scrubbing technology. “It helps make sure patients feel safe,” said Williams. Upgraded and new air filtration technology can also help practice staff feel safer on the job. 
• Remain flexible. A growing body of research is demonstrating the role air scrubbing technology can play in combatting COVID-19, but there is still more to be discovered about the virus and how to best control its spread. “There needs to be more information out there about how dentists should be approaching purchasing these devices,” said Shahhal. “My advice is to continue to educate yourself on the coronavirus and, as more information comes out, understand how we can be protected.”

While more research will emerge, it is important to remember that air filtration is just one, albeit important, tool at dentists’ disposal. Investing in HVAC upgrades and standalone air filtration units must go hand in hand with the other evolving safety protocols outlined by regulatory agencies.

Carrie Pallardy is a freelance writer and editor based in Chicago. To comment on this article, email impact@agd.org.

References
 
1. Versaci, Mary Beth. “Products Marketed to Sanitize, Reduce Dental Aerosols May Lack Research to Support Efficacy.” American Dental Association, 22 May 2020, ada.org/en/publications/ada-news/2020-archive/may/products-marketed-to-sanitize-reduce-dental-aerosols-may-lack-research-to-support-efficacy. Accessed 7 Dec. 2020. 
2. “Scientific Brief: SARS-CoV-2 and Potential Airborne Transmission.” Centers for Disease Control and Prevention, 5 Oct. 2020, cdc.gov/coronavirus/2019-ncov/more/scientific-brief-sars-cov-2.html. Accessed 7 Dec. 2020. 
3. Zhao, Bin, et al. “Using an air purifier as a supplementary protective measure in dental clinics during the coronavirus disease 2019 (COVID-19) pandemic.” Infection Control & Hospital Epidemiology, 11 June 2020, DOI: 10.1017/ice.2020.292. 
4. “Air Cleaners, HVAC Filters, and Coronavirus (COVID-19).” United States Environmental Protection Agency, epa.gov/coronavirus/air-cleaners-hvac-filters-and-coronavirus-covid-19. Accessed 19 Nov. 2020. 
5. Heffernan, Tim. “Can HEPA Air Purifiers Capture the Coronavirus?” Wirecutter, The New York Times, nytimes.com/wirecutter/blog/can-hepa-air-purifiers-capture-coronavirus/. 18 Nov. 2020. 
6. “Guidance for Dental Settings.” Centers for Disease Control and Prevention, 4 Dec. 2020, cdc.gov/coronavirus/2019-ncov/hcp/dental-settings.html. Accessed 7 Dec. 2020. 
7. “Indoor Air Quality (IAQ): What is a HEPA Filter?” United States Environmental Protection Agency, epa.gov/indoor-air-quality-iaq/what-hepa-filter-1. Accessed 19 Nov. 2020. 
8. “UV Lights and Lamps: Ultraviolet-C Radiation, Disinfection, and Coronavirus.” U.S. Food & Drug Administration, fda.gov/medical-devices/coronavirus-covid-19-and-medical-devices/uv-lights-and-lamps-ultraviolet-c-radiation-disinfection-and-coronavirus. Accessed 19 Nov. 2020. 
9. “Air Purifier Buying Guide.” Consumer Reports, 9 March 2020, consumerreports.org/cro/air-purifiers/buying-guide/index.htm. Accessed 7 Dec. 2020.