Measurement of ultraviolet (UV) radiation for disinfection applications


UV-C radiation has recently received widespread attention from the general public, since it can be used to disinfect surfaces potentially contaminated by the SARS-CoV-2 virus, which causes the coronavirus disease (COVID-19).  Though UV-C light sources have already been used for disinfection for a long time, the current situation has led to introduction of a wide range of UV-C sources to the market. Triggered by these developments, CIE, the International Commission on Illumination, has issued a position statement on the application of UV radiation for managing the risk of COVID-19 transmission [1]. In this position statement CIE stresses the importance of health and safety issues related to the application of UV-C for disinfection and the need for appropriate UV-C measurements. VSL actively participates in division 2 of CIE, which is responsible for physical measurement of light and radiation and offers a wide range of calibration services related to light and lighting.

UV-C radiation from 200 nm to 280 nm, is part of the UV spectrum commonly referred to as ‘germicidal UV’ (GUV), because of its application for germicidal purposes. GUV also covers UV-A radiation (315 nm – 400 nm) and UV-B radiation (280 nm – 315 nm), but UV-C is most commonly applied, since it has the highest energy and therefore is most effective in deactivating micro-organisms and viruses. UV-C has been applied successfully for over 70 years for disinfection of water, air and surfaces. In particular, radiation at 254 nm, emitted by low pressure mercury lamps, is widely used.  More recently, also UV-C light emitting diodes, emitting radiation between roughly 260 nm and 280 nm are applied for disinfection purposes.  UV light is effective in disinfection because it can damage the structure of the DNA of cells or cause malfunctions in cell structures, such as its membrane. Because of that, exposure to UV light deactivates the infectious potential of bacteria and viruses. On the other hand, UV-radiation may also cause damage to cells in the human body and, as a consequence, exposure to UV light might cause serious diseases in healthy people. UV-C sources can be very hazardous to the eyes and skin and exposure should be avoided, unless clinically justified.

When applying UV-C radiation for disinfection, two aspects are important: safety and the effectiveness of the disinfection. Appropriate quantitative measurement of the emitted UV-C radiation is therefore essential. Clearly, the source should deliver the required dose (and wavelength) that is needed for effective disinfection, but measurements may also be needed for safety reasons, e.g. to determine whether the radiation is properly shielded by an enclosure or to know at which distance an operator can safely use such light source. CIE therefore stresses that radiometers that are used for measuring UV-C should be calibrated, preferably by an accredited laboratory, to ensure traceability to the international system of units (SI) and to guarantee comparability and reliability of measurement results. Even when a radiometer has been calibrated and a certificate is available, one must be aware of potential measurement errors that may occur, especially when the radiometer is used for measuring radiation from different types of light sources. Typically, a UV radiometer is calibrated for measuring the power per unit surface emitted by specific light-source, e.g. a low-pressure mercury lamp at a particular distance. When applied for measuring other sources (e.g. UV-C LED sources) large errors may arise, due to the different spectral distribution of the source. 

In case you have any queries about measurements of UV radiation, or when you have an instrument that needs to be calibrated, please contact us via email: or phone: +31 15 269 1500. 

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