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Enhancing Air Filtering in Ambulances to Reduce Covid-19 Aerosols

British health and engineering experts are recording and analyzing the airflow in modern ambulances to help reduce the potential exposure of ambulance crews to Covid-19 aerosols in their vehicles.

The study is being carried out by Cranfield University, the University of Cambridge, the commercial company Q-Flo and the National Health Service in England. It is funded by the Royal Academy of Engineering, the UK’s national academic body for the field. Professor Helen Atkinson, pro-vice-chancellor of aerospace, transport and manufacturing at Cranfield University, is overseeing the project. She said:

“There are currently nearly 30,000 paramedics in the UK and thousands of ambulances nationwide. Airflow patterns inside ambulances are complex and not well documented. Mapping these flows will enable the optimized installation of filtration systems and reduce the potential exposure of NHS ambulance crews to Covid-19 aerosols in their vehicles.”

Researchers will explore how the airflow changes in different driving conditions, taking into account factors including speed and weather. The project will provide flow maps from the ambulance interior over a range of driving conditions up to 70 mph. Covid-19 aerosol sizes, that can be inhaled, are generally less than 10 microns in diameter and particles of this size tend to follow flow patterns without settling onto surfaces.

Dr. Adam Boies, Reader in the Department of Engineering at the University of Cambridge and partnership director in the Aerosol Center for Doctoral Training, said:

“Effective filtration strategies for PM10 particles are increasingly seen to return environments to safe levels of operation following viral release whereby suspended particles that remain after droplet drying may remain indefinitely without dilution or active removal.”

The flow data being collected will facilitate the integration of an active virus filter (AVF) system known as TorStranTM, developed by Q-Flo Ltd. This takes in contaminated air and captures individual virus molecules, including those contained in airborne droplets, then destroys the virus molecules and returns clean air to the environment.

Martin Pick, Chief Operating Officer of Q-Flo, said the project was “perfectly timed.” He added:

“It will help to keep people safe, reducing the risk of infection, but it is critically important that we understand where to position the unit to ensure maximum effectiveness.”

Rollout in the Next 12 Months

Knowledge of the flow field is key to allowing experts to effectively integrate their filtration system into NHS ambulances. The current Q-Flo filtration design is at an advanced phase, meaning a significant rollout of the product could occur in the next 12 months. Work to collect the data is already underway and a flexible mounting system for the light source and imaging system has been fitted inside an ambulance interior.

Calibration and testing of the flow visualization system in a stationary and moving ambulance has already begun, enabling the acquisition of image datasets from selected regions of the vehicle.

Phil Pimlott, assistant director of operations at South Central Ambulance Trust NHS said:

“We are very pleased and excited to be involved with this project and are fully committed to working with the group in an area that has been a challenge for ambulance services and the NHS for numerous years. The success of this project will be extremely positive for the patients we carry and care for and will assist our ambulance crews across the UK and potentially the world in delivering the highest care they can give to patients.”

Airflow patterns inside ambulances are complex and not well documented.


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  • Katherine Whelan