As a result of changes to practice aimed at reducing the risk of transmission of COVID-19, the clearance of infectious particles (“fallow time”) following an AGP needs to be considered, and this is dependent on the ventilation and air change within the room.
Dental guidance documents from various agencies have been published regarding fallow time. Members are advised to review these guidelines and standard operating procedures (SOPs), including the CDO guidance for their jurisdiction. This guidance should be taken into account when calculating the rate of clearance and considering any reduction in fallow time.
The FGDP guidance states, ‘mitigating measures may be implemented to reduce this figure’ and highlights the importance of having clear evidence of undertaking a risk assessment of the operating environment if the fallow period is to be reduced.
Types of air change
Dental Protection has sought clarification from Public Health England regarding the use of air purification and air exchange. It is their understanding that there are different ways to ‘change’ the air in a room:
- Natural ventilation – open a window
- Negative pressure room through mechanical ventilation is where air is actively sucked from the room - pulling in fresh air from outside (like isolation rooms)
- Positive pressure room through mechanical ventilation - Air is pushed into the room and let out of vents above floor level and out of other openings such as doors.
- Changing the air through ‘cleaning the air’ through HEPA filters/ UV filters – These devices are typically recirculating units which enhance the effective air change rate by removing or inactivating airborne virus.
Any ventilation system used should be set to provide the maximum amount of fresh air and the
maximum number of air changes it is able to provide. The use of air purifiers / air cleaners containing a HEPA filter and/or other adjuncts has been suggested in reducing the clearance time of potentially infective aerosols. In respect of devices that are designed to remove viable microbes by filtration or microbicidal action, the guidance states it is difficult to make general recommendations because of the variability in the rate they pass air through the device and also because the efficacy may be affected over time as filters become blocked or UV emission in microbicidal devices changes. Therefore, each device needs to be validated by the manufacturer and maintained.
“In room”, recirculating HEPA filter units and recirculating UV irradiation units (also known as “air scrubbers”) do not provide fresh air into the space and careful selection of the unit is required to ensure they filter out the appropriate size of aerosol or particulate. We have been advised that “recirculating air cleaning devices based on HEPA filter systems or UV-C are likely to be effective”.
Practice owners who wish to use air-purification or air exchange devices should undertake a risk assessment which takes into account: the manufacturer’s instructions, the size of the surgery, the type of unit used and any independent evidence to support any reduction in fallow time.
What about indemnity arrangements?
The provision of a safe environment within the surgery is a health and safety issue and members should at all times seek assurance from their commercial/business insurance providers that their public/employer liability policies extend to cover any claims which arise as a result of using an air purifier/filtration system or air exchange technology. We would expect these claims to fall to Employers’ Liability or Public Liability insurance as they do not relate to clinical negligence.
In order to be able to defend a claim, practices should be able to show that a decision to reduce fallow time was evidence based. Information regarding the risk assessment should be retained and may be requested should a claim arise.
Members would be entitled to request assistance in relation to any allegations that relate directly to the provision of the patient’s clinical treatment. Members can be reassured that they can request assistance in relation to any non-claims support, for example a complaint being made to the GDC, arising from the use of such systems.