Spectral Characteristics and Indoor Air Quality Effects of Germicidal 254 nm and 222 nm Ultraviolet Light

Published

November 27, 2024

Author(s)

Michael Link, Andrew Shore, Rileigh Robertson, Behrang Hamadani, Dustin Poppendieck

Abstract

Current Germicidal Ultraviolet (GUV) devices are designed to inactive pathogens in air at either 222 nm or 254 nm wavelengths. Previous research has demonstrated both wavelengths can produce oxidants in air (222 nm: ozone, 254 nm: hydroxyl radicals) and potentially directly photolyze some chemicals. This study sought to determine the impacts of GUV devices on indoor air chemistry in both laboratory chamber and field settings. To ensure the devices were operating using wavelengths and intensities of interest, spatial spectral irradiance measurements of one 222 nm (GUV222) and one 254 nm (GUV254) device were performed. Chamber testing to determine air quality impacts consisted of operating the above devices for four hours in a sealed chamber containing six challenge chemicals. Field testing consisted of operating the devices in an unoccupied restroom on the NIST campus. Ozone, formaldehyde, other volatile organic chemical (VOC) oxidation products and ultrafine particles were measured for each device in each scenario. In chamber experiments GUV254 generated formaldehyde and likely directly photolyzed an equivalent amount of acetone, contributing to a minimal net change in VOC oxidation products. In addition, GUV254 generated measurable ultrafine particles in the chamber experiments, albeit less than GUV222. For GUV254, formaldehyde, VOC oxidation products, ultrafine particles and ozone generation were not measurable in the restroom. In both the chamber and restroom installation GUV222 generated ozone, VOC oxidation products and ultrafine particles. GUV222 generated quantifiable formaldehyde in chamber testing only. GUV222 was demonstrated to directly photolyze tetrachloroethylene in the chamber. Lastly, to better understand the irradiance spectrum in indoor spaces where GUV devices may be deployed, spatial and temporal changes to the 375 nm to 850 nm spectrum was examined at the NIST Net Zero Energy Residential Test Facility (NZERTF). A measurement location near a window was compared to measurement close to an internal ceiling. Indoor diurnal total irradiance and spectrums collected near the spring equinox and summer solstice were compared.

Citation

NIST Interagency/Internal Report (NISTIR) - 8550

Report Number

8550

NIST Pub Series

NIST Interagency/Internal Report (NISTIR)

Pub Type

NIST Pubs

Download Paper

https://doi.org/10.6028/NIST.IR.8550

Local Download

Keywords

Germicidal Ultraviolet (GUV), ozone, formaldehyde, 222, 254

Citation

Link, M. , Shore, A. , Robertson, R. , Hamadani, B. and Poppendieck, D. (2024), Spectral Characteristics and Indoor Air Quality Effects of Germicidal 254 nm and 222 nm Ultraviolet Light, NIST Interagency/Internal Report (NISTIR), National Institute of Standards and Technology, Gaithersburg, MD, [online], https://doi.org/10.6028/NIST.IR.8550 , https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=958820 (Accessed December 12, 2024)