What’s the difference between UV-C and Far-UVC?

If you've looked into UV products, you might have noticed two different options: UV-C and far-UVC technology.

Both types of products use wavelengths within the UV spectrum to disinfect air and surfaces, so what's the difference between them? Can they both be used in the fight against COVID-19?

The largest difference is most UV-C products use 254 nanometer light and most far-UVC products use 222 nanometer light.

What is UV-C?

Scientists discovered UV-C (also called germicidal UV) more than a century ago. Since then, it's been studied and used in applications like water treatment and preventing the spread of pathogens in hospitals.

The UV-C spectrum includes wavelengths from 200 to 280 nanometers. These wavelengths are known for the ability to eliminate 99.9% of pathogens, such as viruses, bacteria, fungi, and mold spores.

Most traditional UV-C products (like low pressure mercury lamps) use energy from the 254 nm wavelength because scientists found it the most effective. UV-C LEDs, which are relatively new to the market, are generally 260 to 280 nm. Other products use broad spectrum UV, which is a combination of wavelengths found in UV-A, UV-B, and UV-C ranges.

Recently, scientists found UV-C light can kill SARS-CoV-2, the virus that causes COVID-19. More businesses have started to add UV-C products to protect their employees, tenants, and customers.

What is far-UVC?

Researchers started focusing on far-UVC in the last decade. Far-UVC uses a lower range of wavelengths (between 207 and 222 nm) for disinfection. Most far-UVC products contain 222 nm light.

When you ask experts in the lighting industry about far-UVC, there is mixed reaction. Some experts believe far-UVC is safe for humans. Others say there is not enough evidence to back up those claims.

Dr. David Brenner, a scientist at Columbia University, started talking about the benefits of far-UVC several years before the COVID-19 pandemic.

Dr. Brenner gave a TED talk about the benefits of far-UVC against superbugs like coronaviruses and the flu. He believes far-UVC is a tool that can be used to limit the transmission of SARS-CoV-2 in public places.

Dr. Brenner is continuing his research on far-UVC and just released a study in June explaining how far-UVC kills coronaviruses.

The International Ultraviolet Association is taking the opposite approach and believes far-UVC is not ready for widespread applications yet. Their argument is based on limited testing on humans.

However, scientists are starting to test far-UVC on humans. A study published in August 2020 tested the safety of 222 nm light on human skin. Scientists exposed patients at hospital in Japan to doses as high as 500 mJ/cm2 .

To put that in perspective, the current threshold limit for far-UVC products is between 22 and 23 mJ/cm2 .

UV-C products vs. Far-UVC products

Now that you know the pros and cons of UV-C and far-UVC, how do they really stack up against each other?

Here's a comparison chart:

We will most likely see more far-UVC products on the market in the months and years to come as more manufacturers focus on the technology. Scientists are continuing their research into safety.

Meanwhile, UV-C products continue to be a solid and reliable source of disinfection for a wide range of industries, including hotels, retail stores, restaurants, schools, and more.