As early as the nineteenth century, researchers had discovered that viruses are sensitive to heat radiation and UV light. Interest in disinfection without the use of chemicals is now growing, particularly in light of the current situation. Can UV light help in the battle against COVID-19? Coronaviruses were first identified in the mid-1960s, and earlier outbreaks such as SARS (Severe Acute Respiratory Syndrome) have caused fear among populations worldwide. Experiments have shown that this virus is also sensitive to UV-C light: with an irradiance of more than 90 μW/cm2 and the corresponding irradiation period, coronaviruses have previously been curbed considerably.
Even though it is not certain whether UV light can be used to prevent pandemics, it is already currently being used intensively in the hygiene sector to disinfect water and surfaces [AUVL]. Generally, microorganisms with simple structures are highly sensitive to UV radiation; and in the case of fungi or spores, higher levels of energy or longer irradiation periods are required to deactivate them. An important parameter in this context is the radiant exposure (J/m2), which specifies the incident energy per unit area and is calculated as temporally integrated irradiance (product of irradiance (W/m2) and time (s)). Depending on the type of microorganism, the minimum dose must be determined and this amount, at least, must be observed. Fundamental strategies with regard to universal application against COVID-19 still have to be researched in more detail.
For a long time, mercury vapour lamps produced UV-C light, triggering biochemical reactions in microorganisms and killing them. For the future, manufacturers are increasingly relying on UV-C LEDs with wavelengths ranging from 250 to 300 nm, since they offer advantages such as a long service life, they can be dimmed, and peak wavelengths can be optimally adjusted. However, as with any kind of research, success is preceded by intensive studies and measurements.