top of page


What is Biological Inactivation?

Biological Inactivation is a process whereby pathogen particles (Microorganisms such as Viruses, Bacteria, Mycoplasma and Fungi) are destroyed and cannot divide and multiply, and therefore cannot cause farther infection. Depending on the level of destruction, pathogens may maintain some of their integrity to be recognized by our immune system and evoke an adaptive immune response to create a natural protection of our body against these microorganisms.

Biological Inactivation by Ultraviolet (UV) Light

Ultraviolet (UV) Light sources have been used for Airborne and Surface Biological Inactivation for many years. Light wavelength within the short-wave, or C band of the UV light (UVC) were found to be the most effective germicidal light wavelengths. UVC usually is generated by use of UVC fluorescent lamp. These lamps use electrical discharge through low-pressure mercury vapor enclosed in a glass tube that transmits UVC light (primarily at the mercury wavelength of 253.7nm). Because this wavelength has been found to be about the optimum for killing microorganisms, UVC from mercury lamps also is referred to as UVG to indicate that it is germicidal. UVG has been shown to inactivate viruses, mycoplasma, bacteria and fungi when used appropriately.

How does UVC light inactivate pathogens?

The mechanisms of UVC light on microorganisms are uniquely vulnerable to light at wavelengths at or near 253.7 nm because the maximum absorption wavelength of a DNA molecule is 260 nm. After a certain amount of UVC light dose (irradiation) is administered, the light initiates a reaction between two molecules of thymine, one of the bases that make up DNA (or Uracil, one of the bases that makeup RNA). The resulting thymine dimer is very stable, but repair of this kind of DNA damage--usually by excising or removing the two bases and filling in the gaps with new nucleotides--is fairly efficient for human cells, but not possible in viruses, so damage is extensive and permanent.

According to the types of the nucleic acids, viruses can be divided into four groups, including single-stranded RNA (ssRNA), single-stranded DNA (ssDNA), double-stranded RNA (dsRNA), and double-stranded DNA (dsDNA). Studies have shown that ssRNA require lower dose of UVC light to be inactivated while progressively ssDNA, then dsRNA and last dsDNA will require more UVC dose to achieve inactivation.  

The amount of UVC irradiation and dose to achieve inactivation varies among the virus types.

A large number of research projects exists on this subject, some is enclosed here in our "Research Documents" section below. 

In general, the radiation intensity (irradiation) is measured in W/m^2 (Watts to Meter square). It represents the amount of energy that the UVC light source generates. This energy decreases along the radial direction moving away from the light source. 

The amount of energy over time delivered to the virus is the Dose. Dose is measured in J/m^2 (Joule to meter square).

An example for SARS-CoV-2 virus that cause the Covid-19: a 3mJ/cm^2 dose is required to achieve a 99% inactivation.

 The conversion between W to J is done by introducing time element.

1 W/m^2 for duration of 1 Second = 1J/m^2.

In the research document section, you will find the amount of J/m^2 (or in mJ/cm^2) needed to inactivate or damage the RNA/DNA of a % of the virus population which will not be able to replicate or cause farther infection. 

Indication such as 90%, 1 Log or D90 mean that the dose indicated is sufficient to inactivate 90% of the viral population.

99% or 2 Log, 99.9% or 3 Log, 99.99% or 4 Log are other levels of viral depopulation.

How much UVC Irradiation and Dose are needed to achieve a virus inactivation?

bottom of page