The requirement for fallow time post Aerosol Generating Procedure (AGP)

Information on the requirement for fallow time post Aerosol Generating Procedure (AGP) is extracted from the Chief Dental Officer England letter dated 28/08/2020 (click 'read more'). This fallow time significantly reduces the number of appointments a clinician can offer to patients, and therefore also reduces the amount of work a dental laboratory will likely receive.

Public Health England (PHE) have confirmed that the requirement for fallow time is still in place as set out below and in appendix 1 of the Transition to Recovery SOP.

Therefore, we continue to operate against a backdrop of sustained community transmission, and we continue to follow the guidance as published by Public Health England.

Therefore, in acknowledging that drops, splatter and aerosol particles bearing COVID-19 can be generated during dental procedures and to minimise the hazard and risk to dental staff and subsequent patients the following guidance remains:

A post AGP downtime or 'fallow period' is required for droplets to settle and 99% of respirable particles (droplets and aerosols) released during the AGP to be removed from the air.

• Fallow time is calculated from the point that the AGP ceases; not the end of the patient appointment time.

- FFP2 /3 masks and PPE must be worn by any staff operating in or reentering the surgery setting during the fallow time.

- Subsequent patients should not enter the surgery until the fallow time has fully elapsed.

• The length of the fallow time is determined by the room's ventilation parameters:

- Most dental surgeries are neutral pressure rooms. Windows in neutral pressure rooms should be opened, or extractor fans that vent to the exterior should be used as air passing externally will be highly diluted and is not considered to be a risk. It is recommended that the room is left vacant for one hour for a neutral pressure room after cessation of the AGP before cleaning is carried out.

- For dental surgeries with ventilation systems these should be set to provide the maximum amount of fresh air and the maximum number of

air changes. In a treatment room with 10-12 air changes per hour (ACH), a minimum of 20 minutes post APG is considered pragmatic. In a single room with 6 ACH this would be approximately one hour.

Practices are advised to undertake a systematic review of their dental practice's current ventilation processes. If you are unsure of the air changes and capacity of ventilation-filtration systems in your dental practice, then you must seek advice from the manufacturers of your ventilation systems and the contracted maintenance team to confirm current ACH capacity. Further information and advice should be sought

from your local Environmental Health Teams.

On Tuesday 4 August 2020, National Services Scotland published a Short Life Working Group technical report into 'Ventilation, water and environmental cleaning in dental surgeries relating to COVID-19' . As stated at the start of the technical report the publication is 'not intended as specific formal guidance'. The technical report will be considered as part of the wider evidence review by SDCEP and will inform their

recommendations for the development of guidance in England. Following publication of the SDCEP review, OCDO will be working with PHE to further develop guidance for dental practices in England with a focus on fallow time.