Intercomparison of Instruments Used for Safety and Performance Measurements of Ultraviolet Germicidal Irradiation Lamps

Abstract

Public health concerns such as multidrug-resistant tuberculosis, bioterrorism, pandemic influenza, and sick building syndrome have brought about increased interest in the use of ultraviolet germicidal irradiation (UVGI) to prevent the spread of airborne infection. UVGI lamps require that radiometric measurements be performed to ensure their safe and effective use. This study evaluates 10 detectors that measure the ultraviolet radiation hazard of low-pressure mercury UVGI lamps, including a polychromator spectroradiometer, narrowband detectors designed to measure the ultraviolet radiation in a short range of wavelengths, and broadband detectors with a varying spectral response designed to follow the UV hazard action spectrum. The angular responses, spectral responses, and linearity of the detectors were measured and compared. The agreement between the measured angular responses and the ideal cosine responses varied widely among the detectors, and in general, the detectors with diffusing optics agreed significantly better with the ideal cosine response. The spectral responses at 254 nm also varied widely among the detectors, and, in general, the narrowband detectors agreed more closely with the 254 nm irradiances measured under the same conditions by a double monochromator spectroradiometer. All detectors displayed good linearity. The angular and spectral response data were then used to develop correction factors for the effective irradiance measurements of two UVGI sources, each measured at 10, 20, and 30 cm. The measured effective irradiances were compared with those measured by a double monochromator spectroradiometer with an integrating sphere input optic. Prior to correction, the effective irradiances measured by the detectors varied widely, ranging from 0.29 to 2.7 times those measured by the spectroradiometer. The application of cosine and spectral response correction factors significantly improved the agreement for the effective irradiances measured by all of the detectors, typically to within 10-20%. Awareness of these detector characteristics can play a key role in ensuring the accuracy of health hazard measurements of UVGI lamps.

Guidelines on the measurement of ultraviolet radiation levels in ultraviolet phototherapy: report issued by the British Association of Dermatologists and British Photodermatology Group 2015

“…Silicon photodiodes have a spectral response extending over UV wavelengths, visible light and near‐infrared radiation. At shorter UV wavelengths, vacuum photodiode sensors are often employed . Gallium arsenide phosphide photodiodes are also effective UV sensors .…”

“…A special example of a filter‐modified response is that of a radiometer with a net spectral response mimicking the hazard‐weighted action spectrum. This can be achieved with a vacuum photodiode sensor and a matched filter . Such radiometers can be calibrated to indicate directly hazard‐weighted irradiances with acceptable accuracy, irrespective of the exact emission spectra of the UV source.…”

“…For routine phototherapy work, a deviation of < 2% from true linearity has been recommended . Safety measurements around UV phototherapy equipment are particularly demanding of dynamic range and linearity, but higher‐quality radiometers are likely to offer sufficient performance …”

Ultraviolet spectral irradiance measurements: an intercomparison of spectroradiometers in laboratory combined with a workplace field test

“…For this work, we choose a more practical approach. The aim was to check the comparability of spectroradiometers (and radiometers) within the European occupational safety community in their actual state to account for every day usage with UV radiation sources like lamps or welding arcs [16,17] and to allow the reader to decide on his own which device to use for what purpose (laboratory or field measurements). Consequently, the present article does not deal with the topic of measuring uncertainty but with an intercomparison of five different types of spectroradiometers regarding their measuring accuracies of absolute UV irradiance and their wavelength misalignments.…”

Stray light correction on array spectroradiometers for optical radiation risk assessment in the workplace

“…Due to the variety of sources and the wide range of the spectrum, there are no accurate, fast, simple, and affordable methods for measuring risk in the workplace. Radiometers can rapidly measure an entire wavelength region [12]; nevertheless to avoid errors, the radiometer should be calibrated with a standard source similar to the tested source [13,14]. This is unconceivable, as radiometers are intended to measure various types of sources in the workplace.…”