Frequently asked question

UVC refers to the invisible light with wavelength 100nm to 280nm. For disinfection purposes, UVC with wavelength from 100 – 200 nm will produce toxic Ozone in the air. 265nm UVC is considered the most effective as DNA and RNA absorbs its energy the most. UVC energy is absorbed by nucleic acids inside the RNA and DNA of the microbes, resulting in covalent bonds which at the right dose can render the pathogen unable to reproduce and infect.  The principal way UVC inactivates a pathogen is the creation of Thymine dimers within the cell DNA – which has a demonstrated peak absorption of 260 nm.

Why are these absorption spectrums slightly different across pathogens? This change is the result of cellular protein, specifically the presence of aromatic amino acids. UV Dose is the amount of UV radiation a microbe is exposed to and depends on the intensity of UV radiation and exposure time. A number of biological studies have produced widely accepted typical UV dose requirements for most common target microbes in disinfection.

How much time do I need to disinfect

  • a phone: phone surface contains the following germs: Streptococcus, MRSA and E. coli. To inactivate streptococcus, on average you need 5sec; for MRSA that is ___ seconds; for E.coli – ___ seconds. Add here a video sample of germs from the phone and Sterfly effect on them.—Application-Note—AN002.pdf

  • a mask: While different viruses and bacteria need different doses for inactivation, on average it is about 5 seconds within 5 cm distance. The closer it is, the higher the UVC dose, hence, shorter time for disinfection needed. Once disinfected, the mask can be used again. (Reference 1). Also, Sterly can sanitize the bacteria inside the mask that cause bad smell.


According to CDC and the University of Nebraska developed an N95 Filtering Face Mask Respirator Ultraviolet Germicidal Irradiation (UVGI) Process for Decontamination and Reuse (source), UVC can be used for masks disinfection without damaging the material of the masks.


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With 5cm distance Sterly can inactivate germs on average in 5 – 10 seconds. The time needed to disinfect germs decreases significantly with a closer distance 

Normally, you want to keep the UVC torch within 5cm distance to the disinfecting objects. The closer you point Sterly to the item, the more powerful UVC dose the item gets, hence, it inactivates microbes faster.

As Sterly is a powerful device. We strongly recommend you not to use Sterly for more than 5min of continuous disinfection.

No, UVC will be absorbed by mostly all kinds of surfaces and no reflection can occur. Video showing for the dose of UV pointing to a mirror.

For many years, UV mercury lamps were considered to be the best choice. However, lamps have several limitations, including low activity at refrigeration temperatures, fragile construction, long warm-up time, risk of mercury exposure, and limited UV emittance at 254 nm. On the contrary, UV light-emitting diodes (UV LEDs) do not contain toxic mercury, work instant and emit at optimal UV wavelength of 265nm for disinfection. UVC LEDs are compact, durable and well suited to battery powered operation for point-of-care tools and mobile healthcare equipment.

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