FAQ

Ultraviolet germicidal irradiation (UVGI) is a disinfection method that uses short-wavelength ultraviolet (UV-C) light to kill or inactivate microorganisms by destroying nucleic acids and disrupting their DNA, leaving them unable to perform vital cellular functions. UVGI is used in a variety of applications, such as food, air, surface and water purification.

UV light is electromagnetic radiation with wavelengths shorter than visible light but longer than X-rays. UV is categorised into several wavelength ranges, with short-wavelength UV-C considered "germicidal UV". Wavelengths between about 200 nm and 300 nm are strongly absorbed by nucleic acids. The absorbed energy can result in defects including pyrimidine dimers. These dimers can prevent replication or can prevent the expression of necessary proteins, resulting in the death or inactivation of the organism.

References and more information on UVGI can be found here.

Li.LAC uses two low pressure mercury vapor lamps that emit UV light at a wavelength of 254nm (253.7nm to be exact).

The effectiveness of disinfection through UV-C depends on the duration of exposure, the intensity and wavelength of the UV radiation and the microorganism's ability to withstand UV during its exposure.

In air and surface disinfection applications the UV effectiveness is estimated by calculating the UV dose which will be delivered to the microbial population.

The UV dose is calculated as follows:

UV-dose H [mJ/cm2] = UV-irradiance E [μW/cm2] × exposure time [seconds]

The threshold dose H90% [mJ/cm²] for inactivation of different organisms (LD90, 90% inactivation) with UV radiation of 254nm can be found e.g. in DIN 5031-10:2018-03.

Examples according to DIN 5031-10:2018-03 are:

For example for bacteria Staphylococcus the reduction at dose H is:

The UV-C irradiance inside Li.LAC was tested and verified at the accredited test laboratory Opsytec Dr. Gröbel GmbH (DAkkS registration number: D-PL-20284-01-00). According to the test certificate the lowest irradiance inside Li.LAC is: Emin = 373µW/cm².

After a 5 minute exposure the minimum dose inside Li.LAC calculates to:
H5min = 373µW/cm² x 300s = 112mJ/cm²

According to the above mentioned literature values, bacteria and viruses are inactivated to >99.99% after 5 minutes of irradiation inside Li.LAC.

Microbiological tests were not performed. This evaluation is transferable to other microorganisms based on literature data (for example DIN 5031-10:2018-03).
OSRAM provides a list of LD-90 (90% inactivating) doses for various microorganisms. NB: the values in the table on page 4 are in [Ws/m²] = [J/m²], 1Ws/m² = 1J/m² = 0.1mJ/cm².

Recent studies (here or here) show that the irradiation dose for inactivating 90% of corona viruses is between 4mJ/cm² and 12mJ/cm². Following the example calculation above, the dose for inactivating 99.99% of corona virus calculates to:
H99.99% = 4x 12mJ/cm² = 48mJ/cm²
The lowest UV-C dose inside Li.LAC after 5 minutes is well above this required value.

Yes, there is.

We wanted to know exactly how well the UV-C irradiation inside Li.LAC would inactivate viruses on the complex surface of a real microphone, including the metal grille and the foam underneath.

The departments Biomedical Engineering and Medical Microbiology & Infection Prevention of the University Medical Center Groningen (UMCG) have conducted comprehensive scientific studies to evaluate the effectiveness of Li.LAC.

Viruses were sprayed onto microphones*, similar to singing into the mic. The results show a reduction of 99.3% of the viral load on strongly contaminated microphones (including the metal grille and foam) after 10 minutes irradiation inside Li.LAC.

Read more

* Industry standard vocal microphones were used for this study.

The longer the UV-C radiation lasts, the better the disinfection.

Roughly one can say that doubling the disinfection time allows a better reduction of germs by about a tenth.
The optical proof of effectiveness for Li.LAC (see FAQ above) shows that after 5 minutes 99.99% of most viruses and bacteria on the surface of the microphone have been destroyed. The virological studies by the University Medical Center Groningen (UMCG - see FAQ above) not only looked at the surface of the microphone, but also at the complex microphone grill and the foam underneath. In these experiments, viruses were sprayed onto the microphone similar to singing into the mic. These studies show a reduction of 99.3% after 10 minutes of irradiation inside Li.LAC.

What does that mean in practice?

The reduction of viruses and bacteria after 5 minutes is already very good. After 10 minutes, the level of disinfection is even better.

If you need the microphone right away because the next performer is already waiting at the stage entrance, then the short program makes sense. If there is enough time, one can use the long program.

The irradiation chamber and the steel grille are optimized for disinfecting up to three handheld microphones or handheld transmitters.

All boundaries of the chamber are coated with aluminium, UV-C-optimized, diffusing mirrors.
The distribution of UV-C energy is NOT homogeneous within the chamber!

The microphone shaft (the lower half of the microphone) is exposed to an irradiation of approx. 350 to 600µW/cm².
This energy is sufficient for reducing microorganisms on flat surfaces (like the mic shaft) without wearing out UV-C sensitive plastic parts like for example the acrylic display glass on a handheld transmitter.

The microphone head (with metal grille and foam) are exposed to a higher irradiation of approx. 800 to 6000µW/cm².
The higher energy and the highly diffusing mirrors of the chamber ensure a sufficient all-side exposure of the metal grille and the foam underneath.

It is important to understand that any kind of shadowing effect (for example by putting too many items into the chamber) will reduce the effectiveness of the disinfection.
This is similar to getting tan lines on your arm because of wearing a watch during the summer.