Application of Lagrangian particle transport model to tuberculosis (TB) bacteria UV dosing in a ventilated isolation room

Abstract

The aim of this work is to define the basis for design guidelines that will minimise the risk of exposure from airborne organisms in hospital isolation rooms. This research employs an algorithm that combines an understanding of the interaction between the room airflow and the ultra violet (UV) system. The airflow in such a room is complex and therefore cannot easily be accounted for by existing design guidance. The main findings were firstly, the mean lifetime of the ventilated particles does not reduce in proportion with increasing ventilation rate. Secondly, an increase in the ventilation rate reduces the effectiveness of ultra violet germicidal irradiation (UVGI) with only a limited increase in the number of particles that are ventilated. Finally, there is a social benefit attached to this project from the point of view of helping people who are vulnerable as well as reducing their risk of being exposed to possible tuberculosis infection. The significance of these findings is to provide the engineer and the architect with an essential tool to ensure good design practice. It is also important to ensure that the methodology can be applicable to most isolation room uses.

Minimizing the exposure of airborne pathogens by upper-room ultraviolet germicidal irradiation: an experimental and numerical study

“…The cover was attached to a rope that extended outside the chamber, and, to achieve UVGI-on conditions, the cover was removed by pulling the rope. Studies have shown that the effectiveness of an upperroom UVGI system is much more obvious at relatively low ventilation rates than at higher rates [18,19,42]. Hence, for our first experimental and numerical study for predicting the inactivation effectiveness of the UVGI system on bioaerosols, an ACH of 2.9 was used for 71 + 6% relative humidity.…”

Modelling the Performance of Upper Room Ultraviolet Germicidal Irradiation Devices in Ventilated Rooms: Comparison of Analytical and CFD Methods

“…As aerosolised microorganisms are generally very small (typically 5 μm in diameter), and can remain suspended in air for many hours, it was not considered necessary to represent them as a separate phase in the CFD model. The inactivation of microorganisms due to the UV is coupled with the scalar transport equation, as shown in Noakes et al [29] …”

Development of a numerical model to simulate the biological inactivation of airborne microorganisms in the presence of ultraviolet light

“…He also concluded that the number of particles removed by ventilation depends on the exhaust grille location, and that baseboard heating during winter months improves room mixing and hence UVGI e ectiveness. Alani, Barton, Seymour, and Wrobel (2001) also used a particle tracking method to determine the UV irradiation dose received by microorganisms in the presence of an upper-room UV ÿeld in a typical TB isolation room. The study demonstrated that increasing the ventilation rate does not proportionally increase the number of particles ventilated, as assumed by fully mixed models.…”