type A2 biosafety cabinet housed the chamber with the samples. The results showed that the
222 nm light eliminated more than 95 percent of the aerosolized H1N1 influenza virus.
A 2020 study (pre-print; under review)
9
aimed to determine the effectiveness of far-UV 222 nm
light on human coronaviruses from subgroups alpha (HCoV-229E) and beta (HCoV-OC43).
During the tests, researchers applied a far-UV dose of 1.2 and 1.7 mJ/cm
2
to aerosolized alpha
coronavirus 229E and beta coronavirus OC43 samples. The 222 nm UV light source inactivated
99.9% of both viruses. Researchers concluded that based on the results of the tests, adhering to
the far-UV exposure limit of 3 mJ/cm
2
/hour would inactivate 99.9% of coronaviruses in public
locations within 25 minutes. Increasing the intensity of the light, e.g. by a factor of 2, would
reduce the required exposure time without exceeding exposure limits. It is important to
highlight that although the tests were not conducted specifically on SARS-CoV-2 strain, the
scientists issued recommendations on using far-UV 222 nm light to eliminate the latest SARS-
CoV-2 coronavirus because all human coronaviruses share similar genome sizes. The genome
size of viruses is an essential determinant of UV radiation sensitivity.
Far-UV 222 nm light has the potential to revolutionize food processing and sanitation
standards. A 2020 study
10
showed that far-UV 222 nm lamps can inactivate
Alicyclobacillus
acidoterrestris
spores, which are known to have high thermal resistance. In food processing
facilities handling juices, the microorganisms also thrive in extreme conditions and can
germinate at low pH levels. Scientists were able to achieve complete inactivation by 5 logs at a
concentrated dose of 2,011 mJ/cm
2
. Compared to mercury-based UV 254 nm lights, non-toxic
222 nm excimer lamps come with lower contamination risks when used in large-scale food
processing.
5.0 UV-C 254 nm
Conventional UV 254 nm contains powerful disinfection properties and is rapidly absorbed by
microorganisms. When using UV 254 nm lights, typically in the form of UV-C fluorescent lamps,
operators must wear protective gear to prevent skin burns and corneal damage.
5.1 UV 254 nm Wavelength Properties
UV 254 nm is within the germicidal range of the UV-C spectrum. Compared to UV-B and UV-A,
this range has up to 2 times more electron volt energy (eV). UV-C 254 nm light is absorbed
rapidly by microbes, contributing to its ability to destroy bacteria and viruses. This UV band is
powerful and can force doubly-bonded molecules to rearrange their structures. Damage
imposed on microorganisms are typically long term or fatal.
Fluorescent fixtures, medium-pressure mercury discharge lights and induction lamps are the
most common types of UV 254 nm artificial light sources used for sanitation. In order to
generate the UV 254 nm band, phosphor is removed from the tube. Furthermore, the tube is
