Vented Individual Patient (VIP) Hoods for the Control of Infectious Airborne Diseases in Healthcare Facilities

A theoretical study on the filtration efficiency and dust holding performance of pleated air filters

Filter media composed of electrostatically charged nonwovens is the key device in an air purifier. Pleated filters are constructed from a cardboard frame with lattice faces containing a filter media reinforce by an expanded support grid, which have more surface area for trapping contaminants and capture airborne contaminants more effectively than non-pleated air filters. The aim of this work is to investigate the dominant factors on the filtration efficiency and dust holding performance of pleated filter by using a modified numerical model. It is found that geometric parameters of pleated filter play important roles to efficiency of the air purifier based on particle loading and filtration efficiency. The stable structural parameters include bending angle of pleated filter material in the range of 0∼60° and the ratio of bending portion less than 0.5. Lower filling degree and shorter length of pleated filter unit exhibit similar stability of efficiency, indicating that the change of structural parameters has little effects on the filtration performance. The knowledge obtained in this work provides concrete reference for the design of high-performance air-cleaner element.

Quantifying the reduction of airborne infectious virus load using a ventilated patient hood

BACKGROUND

Healthcare workers treating SARS-CoV-2 patients are at risk of infection by respiratory exposure to patient-emitted, virus-laden aerosols. Source control devices such as ventilated patient isolation hoods have been shown to limit the dissemination of non-infectious airborne particles in laboratory tests, but data on their performance in mitigating the airborne transmission risk of infectious viruses are lacking.

AIM

We used an infectious airborne virus to quantify the ability of a ventilated hood to reduce infectious virus exposure in indoor environments.

METHODS

We nebulized 10⁹ plaque forming units (pfu) of bacteriophage PhiX174 virus into a ∼30-m³ room when the hood was active or inactive. The airborne concentration of infectious virus was measured by BioSpot-VIVAS and settle plates using plaque assay quantification on the bacterial host Escherichia coli C. The airborne particle number concentration (PNC) was also monitored continuously using an optical particle sizer.

FINDINGS

The median airborne viral concentration in the room reached 1.41 × 10⁵ pfu/m³ with the hood inactive. When active, the hood reduced infectious virus concentration in air samples by 374-fold. The deposition of infectious virus on the surface of settle plates was reduced by 87-fold. This was associated with a 109-fold reduction in total airborne particle number escape rate.

CONCLUSION

A personal ventilation hood significantly reduced airborne particle escape, considerably lowering infectious virus contamination in an indoor environment. Our findings support the further development of source control devices to mitigate nosocomial infection risk among healthcare workers exposed to airborne viruses in clinical settings.