Impact of supplementary air filtration on aerosols and particulate matter in a UK hospital ward: a case study

This article describes a study carried out in an elderly care ward when a portable air filtration unit (AFU) was placed in the central area of the ward. Measurements of carbon dioxide (CO₂) levels and particulate matter (PM) levels were recorded over 2 days when the AFU was in use. The authors were able to compare the measurements when the AFU was turned on with the measurements when the AFU had been accidently turned off for approximately 7 hours. Here are the key points:

• Small aerosol particles are dominant in the transmission of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2).
• CO₂ and PM sensors were installed in central corridor, adjoining corridor, a single room, and the 6-bedded bays.
• Indoor CO₂ levels usually reflects the occupancy of an area as CO₂ is exhaled
• CO₂ correlates positively with respiratory aerosol emissions.
• The measurements of PM and CO₂ levels correlated.
• Particulates up to 10μg in size travelled considerable distance around the ward.
• Staff movement was likely to create turbulent waves aiding PM movement.
• The PM levels of all sizes were positively correlated with indoor CO₂ levels suggesting that activities such as bedmaking and washing patients are likely to generate PM.
• All sensors demonstrated higher levels of PM when the ADU was turned off.
• Use of ACU substantially reduced PM in similar size to respiratory viruses.
• ACU could reduce airborne spread of fungal and bacterial infections including Clostridioidies difficile (formerly named Clostridium difficile).