Indoor Surface Emissions of Volatile Organic Compounds Induced by Germicidal UV (222 and 254 nm) Illumination

The application of germicidal ultraviolet (GUV) lamps has recently attracted increased attention as a measure to mitigate indoor disease transmission. Among the most commonly employed are traditional mercury lamps and krypton–chloride excimer lamps, which emit UV-C light with peak wavelengths of 254 nm (GUV254) and 222 nm (GUV222), respectively. This study investigates volatile organic compound (VOC) surface emissions induced by GUV254 and GUV222 lamps across various surface materials. Near-surface proton-transfer-reaction time-of-flight mass spectrometry (PTR-TOF-MS) measurements revealed significantly increased surface emissions during GUV illumination. In addition to compounds intrinsic to the illuminated surface, GUV light also increased surface off-gassing of externally applied compounds, including limonene and 4-oxopentanal (4-OPA). The magnitude of the enhanced surface emissions was found to decrease with increasing GUV path length resembling the expected decrease of the irradiance. Overall, greater surface emissions were induced by the GUV222 lamp compared with the GUV254 lamp. Conclusively, this study identifies UV-induced surface emissions as a potential source of indoor VOCs during the GUV lamp application.