Inactivation of Airborne Microorganisms Using Novel Ultraviolet Radiation Sources in Reflective Flow-Through Control Devices

Abstract

The goal of this study was to design, test, and model cylindrical flow-through control devices used to inactivate airborne microorganisms with non-mercury radiation sources and a reflective coating, through a broad relative humidity (RH) range. Bench-scale tests determined the effectiveness of three different UV-C sources–light emitting diode (LED), xenon, and mercury. In addition to measurements, modeling was performed that combined photon tracing, computational fluid dynamics, and particle tracking to predict the effectiveness of the respective UV challenges. Regardless of device configuration, UV-induced inactivation of airborne Bacillus subtilis and Mycobacterium parafortuitum was markedly sensitive to low humidity (15 % RH). Actinometry measurements determined that a high reflectance wall coating increased the fluence rate by a factor of 1.6. Predictions of inactivation effectiveness using this hybrid model were in good agreement with experimental observations with errors of less than 15 %.

Acknowledgments

Thank you to Prof. Darin Toohey at the University of Colorado at Boulder for his technical guidance and hardware support. Thank you to Luke Erickson, who helped complete the xenon lamp tests. This work was supported by a subcontract from Kansas State University.

Notes

*Model used microorganism inactivation rates as follows: B. subtilis at 50% RH k = 0.062 (m²/J); at 15% RH k = 0.077 (m²/J); M. parafortuitum at 15% RH k = 0.164 (m²/J).

**Error is calculated as percent difference.