Portable air purifiers could cut Covid-19 transmission in hospital

Cheap portable air filters could cut Covid-19 transmission in hospitals and be a simple way to reduce hospital waiting times as a result of the pandemic, according to UCL and UCLH research.

Aerosol particles are droplets generated from breathing, talking and coughing and are key in the transmission of infectious respiratory diseases like Covid-19. Reducing droplet spread is essential for infection control in high-risk environments such as hospitals.

Research into the use of air filters to reduce droplet spread is being done by teams from the Wellcome / EPSRC Centre for Interventional and Surgical Sciences, UCL Department of Mechanical Engineering, University of Bristol and UCLH. The work is led by Laurence Lovat, Professor of Gastroenterology and Biophotonics at UCL and Consultant Gastroenterologist at UCLH.

Using computational fluid dynamics, the researchers built simulations of UCLH consulting rooms to test the effectiveness of air filters on air clearing. These simulations include two people to mimic the patient-healthcare provider environment.

Overall, the researchers showed that the use of air purifiers can remove up to 40% of potentially infective particles with a single small desktop HEPA (high-efficiency particulate absorbing) filter.

This increases to at least 62% if two purifiers are used. They also examined the importance of the positioning, and found that the filters were most effective when positioned around the same level of breathing (i.e. on a table).

The results suggest that use of air purifiers could be a simple way to increase the number of patients seen in clinic on any given day. At present, patient capacity is limited due to the need to allow time between appointments for clearance of air. Use of air purifiers could therefore help reduce patient waiting times as a result of the pandemic.

Prof Lovat said: "Hospital building engineers are working very hard to find ways to make hospitals safer for staff and patients alike. Use of air purifiers could represent an important mitigation strategy, and one which can be implemented in a simple, cost-effective and rapid way.”

While the UCL and UCLH team’s research has so far focused on consulting rooms, researchers will in future be examining the effectiveness of air filters in waiting areas and hospital wards.

A pre-print paper on work done so far – which is not yet been peer reviewed – was published in November 2021.