COVID-19: Managing Infection Risks During In-Person Dental Care


Royal College of Dental Surgeons of Ontario has published the guideline for their Dental Surgeon and Dental office for preventing the spread of COVID-19 if the dental offices are opening for in-person care. This new guideline is going to be implemented from 25-May-2020 in Ontario. Dentists returning to any degree of in-person care must comply with the direction of government and the College to maintain the safety of patients and staff, and to not contribute to the transmission of COVID-19. All Dental office should require following many precautionary steps including AGP (Aerosol Generating Procedure).

What is Aerosol Generating Procedure?

If the person carrying COVID-19 infection sneeze or cough while in person consultation, the droplet / nuclei generated with potential viruses which get mixed with air and carrying further as airborne contamination.  This airborne contamination may remain suspended in the air for significant periods of time, move with air currents, and encounter others.

This creates a risk for opportunistic airborne transmission of COVID-19, even if the virus is not otherwise able to spread by the airborne route.

While there is no conclusive evidence at this time that opportunistic airborne transmission of COVID-19 occurs after AGPs, the College has adopted a precautionary approach that prioritizes safety.

Droplet Suspension Illustration: – Small droplets produced by potential COVID infected patience
(Courtesy: – ASHREA Position Document on Airborne Infectious Diseases)

How can we prevent the spread at Dental Offices ?

Royal College of Dental Surgeons of Ontario has published the guideline for all Dentists to avoid AGPs whenever possible and use the lowest aerosol-generating options when necessary.

  • Preparing the Operatory for Aerosol-Generating Procedures
  • Use of PPE During Aerosol-Generating Procedures
  • Mitigating High Risk Aerosols
  • Clearing the Air of Aerosol (Fallow Time)

Point 1,2 and 3 are easy to manage for cleaning the office regularly with provided guidelines and wearing health Canada approved PPE. But point #4 is little challenging to achieve.

As per new guideline the operatory must be left empty (with the door closed) to permit the clearance and/or settling of aerosols. The length of time that the operatory must be left empty (the fallow time) is determined by the air changes per hour (ACH). The aim is to achieve 99.9% removal of airborne contaminants.

What is Air Change Per Hour (ACH)?

Number of time displacement of total air volume in given space per hour.

Meaning if you have operatory for 10′ x 10′ size with 8′ height, the volume would be 800 Sq. ft.

Using the following formula, you can derive how many CFM you need to achieve required Air Change per Hour.

Supply CFM = (Volume of the room * Air Change per Hour) / 60

Using this calculator, if you need 10 ACH with 800 volume, you need 133 CFM circulation thru HEPA.

How can you achieve this? 

  • Contact competent HVAC Professional for evaluation to your existing ventilation system.
  • Design appropriate HEPA filter requirement and location in the operatory
  • Retrofit HEPA to the existing HVAC system to purify the air.
  • Certify HEPA filter with Supply CFM & Leak test to ensure the results are positive and compliant with college requirement.

Call us for free consultation with your layout. We will help you to build right solution for you.

What is HEPA Filter?

HEPA:- High Efficiency Particulate Air

High-efficiency particulate air (HEPA) known as high-efficiency particulate absorbing

Filters meeting the HEPA standard must satisfy certain levels of efficiency. Common standards require that a HEPA air filter must remove—from the air that passes through—at least 99.95% (European Standard) or 99.97% (ASME, U.S. DOE) of particles whose diameter is equal to 0.3 μm; with the filtration efficiency increasing for particle diameters both less than and greater than 0.3 μm. See the Mechanism and Specifications sections for more information. HEPA filters are used in applications that require contamination control, such as the manufacturing of disk drives, medical devices, semiconductors, nuclear, food and pharmaceutical products, as well as in hospitals, homes, and vehicles.

How ACH Engineering Can Help you ?

We – ACH engineering has gain extensive experience in providing controlled environment to hospitals, healthcare facilities, pharmaceuticals, pharmacies and many other. Our experts have reviewed the guidelines provided by college and we are confident to provide one stop shop solution to all dental office to meet the requirement.

Upon consultation with us, we will visit your office to collect onsite data – Operatory Room sizes, Existing HVAC evaluation, location for new HEPA filter and other mandatory items. We will develop custom made solution for you which will suits your need as well as your budget.

We can help you to retrofit your existing Dental Office to meet the new guideline and regulations to prevent the spread of COVID-19.