Jonathan A. Otter,1 Louise Clark, 2 Graham Taylor, 3 Amal Hussein, 1 Latchmin Gargee, 1 Simon D. Goldenberg1
1. Directorate of Infection, Guy’s and St. Thomas NHS Foundation Trust (GSTT)
2. Department of Engineering, Essentia, GSTT
3. Authorising Engineer, GPT Consult LLP
Background
Contaminated air can be a vector for the transmission of key hospital pathogens, including respiratory viruses such as SARS-CoV-2. Ventilation in healthcare buildings frequently falls below minimum standards. We evaluated HEPA-based stand-alone air decontamination systems, which offer the potential to reduce risk associated with contaminated air in hospitals, especially where ventilation is inadequate.
Methods
We undertook a structured evaluation of the technical specification of HEPA-based air disinfection systems currently available on the UK market in order to establish the range of manufacturer claims on unit specification and performance. We selected two units for further testing that had sufficient manufacturer-claimed airflow rate to achieve a theoretical 6 air changes per hour in a typical single room. The units were tested to measure airflow rate, noise level at various points in the room and at various settings of the unit, the ability to remove smoke released at various points in the room, the impact on particle count in various points in the room, and a structured engineering review of the unit to include ease of use and maintenance. Testing was undertaken in a single hospital room with a volume of 38m3.
Results
Preliminary testing was undertaken to optimise the room location of the systems. Both units had variable speed settings. The noise level varied from 45 to 80 dBA. Smoke testing showed the units were able to pull in air from most parts of the room. Particle count testing showed that the higher the setting, the more impact on particles that could be identified in the room. The engineering review concluded that both units are relatively low-maintenance.
Conclusions
Our technical specification review narrowed down the wide range of options to those systems that are likely to deliver a meaningful improvement in air quality in hospital rooms. Comparative evaluation of the devices using standardised methods provides useful data to inform decisions about unit selection. The noise levels that we measured were higher than permitted noise levels in hospital wards (35 dBA, HTM-03). Further testing is planned to include more units in a range of room sizes and microbiological air sampling.