Dentists Advised to Mind “Settle Time” After Generating Aerosols

Dentistry Today


The Saskatchewan Health Authority (SHA) advises dentists that “settle time” is the amount of time needed to remove infectious airborne organisms or infectious aerosols created during aerosol-generating medical procedures (AGMPs) from the air in a room.

This time begins when the source of infectious aerosols ends, such as when a patient on continuous airborne precautions is moved out of the room or after an AGMP when a pathogen or virus such as COVID-19 has the potential to be aerosolized during the procedure.

The settle time is used to guide if an N95 respirator needs to be worn while in the room or how long the room must sit before housekeeping can begin cleaning, the SHA said. It never should impact patient care needs or delay essential patient or staff movement in and out of the room, the SHA said.

To determine a specific settle time for a specific room, the number of air changes per hour (ACH) must be evaluated as each room can vary in size, temperature, humidity, ventilation capacity, and other factors. The higher the ACH, the SHA said, the less time is required for settle time.

If the ACH for the patient room is known, a specific settle time can be calculated using an SHA table and posted. For example, if the room has an ACH of 12, the settle time is 35 minutes. Staff then will know how long they must wear an N95 respirator or how long before housekeeping can enter the room to clean. The SHA also advised that the ACH does not reflect the direction of airflow, such as negative pressure versus positive pressure.

If the ACH is unknown, the settle time for a patient room has been determined to be two hours or 120 minutes, the SHA said.

When using a specified settle time, the patient room door should remain completely closed with the exception of essential patient and staff movement. The SHA offers posters that can be displayed on the door. A specific settle time cannot be used if there is a power outage.

Related Articles

CDC Infection Control Guidelines Catch Up With Need to Address Aerosols

TDA Advises Caution as Texas Dental Clinics Reopen on May 1

ADA Updates PPE Guidelines as States Prepare to Reopen