UV-C light is best-known for its germicidal properties. The COVID-19 pandemic has drawn the public’s attention to it due to that. Therefore, you can find many products online that use this band of ultraviolet light to disinfect surfaces and objects.
Yet, not all UV-C light is the same. So, it can behoove you to know the difference if you are on the lookout for disinfection devices using it. By choosing the wrong product, you risk falling victim to false advertising and exposing yourself to germs you may believe you had killed by incorrectly using devices such as cheap UV cleansers.
Two Different Kinds of UV-C Light
UV-C light falls into two categories: the conventional UV-C light (also known as germicidal UV) and far-UVC light.
Both of these bands disinfect surfaces and the air. However, there’s a difference between them. In this article, we’ll explain the differences as well as the pros and cons of each band.
What Is UV-C Light?
Out of the three bands of UV light (UV-A, UV-B, and UV-C), UV-C has the shortest wavelengths, ranging from 280nm to 100nm. In general, the shorter the wavelength, the more damaging the radiation.
In the 1800s, scientists discovered that broad-spectrum UV-C light has the right properties to destroy 99.99% of pathogens such as viruses, fungi, and bacteria by destroying the molecular bonds that hold their DNA and RNA together.
Since then, UV-C has been routinely deployed in healthcare, the food industry, manufacturing environments, water purification companies, fluorescent inspection, and more. In hospitals especially, UV-C light has helped reduce transmission of diseases and eliminated some of the most resistant bacteria.
With the right intensity, distance, and duration, UV-C light can eliminate pathogens in a matter of just minutes or even seconds.
However, the biggest disadvantage of conventional germicidal UV-C light products is that you can only use them in unoccupied spaces or while wearing protective equipment. They are extremely dangerous to human health as careless exposure can lead to burns, cataracts, and skin cancer.
What Is Far-UVC Light?
In the last decade or so, scientists started paying attention to a narrow range of UV-C wavelength known as far-UVC. While conventional germicidal UV-C light has a wavelength of around 254 nm, far-UVC light wavelength ranges between 222 and 207 nm.
Research shows that far-UVC light destroys pathogens as effectively, but without the detrimental effects on human health. There’s a catch, though.
Far-UVC light has a limited range and a strong absorbance in biological materials. Therefore, it cannot penetrate the outer dead-cell layer of human skin or eyes to cause tissue damage.
However, because bacteria and viruses are much smaller than human cells, far-UVC light can penetrate through their DNA and inactivate them.
While this may be a relief, it’s essential to consider that the disinfection process is slow.
While germicidal UV-C light can disinfect an unoccupied space or an area in seconds or minutes, far-UVC light is less intense. As a result, it requires a lot more time to disinfect.
For instance, a study looked at the effects of far-UVC light of 222nm on human coronaviruses. (Not SARS-CoV-2 or COVID-19 specifically, but a range of different human coronaviruses.) The study found out that far-UVC light needed approximately:
- 8 minutes to inactivate about 90% of coronaviruses,
- 11 minutes to inactivate about 95% of coronaviruses,
- 16 minutes to inactivate about 99% of coronaviruses,
- 25 minutes to inactivate about 99.99% of coronaviruses.
Since airborne coronavirus particles can survive in the air for 3 hours or even longer in cold weather, this can be useful in public spaces. However, far-UVC light can be extremely inefficient in handheld devices. After all, will you wait for up to 25 minutes to properly disinfect an area?
Even despite research claiming that far-UVC is safe for humans, some experts in the field still have their doubts. Their biggest concern is that there has been limited testing on the long-term effects on humans, making it inappropriate to be labeled as ‘safe.’
As a result, there are limited products offering far-UVC technology. As scientists continue performing tests and researching safety, we are sure to see more far-UVC products on the market soon. In the meantime, UV-C products continue to be a reliable source of disinfection for many industries.