Far-UVC vs. Multi-Wavelength Antimicrobial Blue Light (aBL): Understanding the Differences Behind the Light

What Is Far-UVC Disinfection?

Far-UVC light, an invisible form of high-energy radiation with a wavelength of approximately 222 nm, has been developed as a technology for reducing airborne pathogens in occupied spaces. These systems usually use filtered krypton-chloride (KrCl) excimer lamps that emit a narrow ultraviolet band designed to limit penetration into human skin and eyes compared with conventional 254 nm UVC sources.

During the COVID-19 pandemic, laboratory and modelling studies indicated that 222 nm irradiation can inactivate aerosolised coronaviruses, including SARS-CoV-2, efficiently at short distances and appropriate doses. This led to increased interest in far-UVC - as well as upper-air 254 nm UVC - installations as part of airborne infection control strategies especially in healthcare settings.

As the acute pandemic phase has passed and ventilation, vaccination and other control measures have become established, the demand for SARS-CoV-2-targeted technologies in healthcare has gradually declined, and attention has shifted towards multi-resistant microorganisms.

In other critical sectors, such as GMP cleanrooms, laboratories and food-production facilities, the main concern is not airborne viruses but bacterial biofilms, equipment surfaces, drains and complex geometries that can serve as long-term reservoirs for contamination. It is therefore relevant to examine how far-UVC and antimicrobial blue light (aBL) perform under these more demanding, surface-related conditions.

Safety Considerations for Far-UVC

Even though 222 nm is considered less penetrating in human tissue than conventional UVC, far-UVC is still subject to strict exposure limits defined by international guidelines. The allowed dose for continuous exposure is low, which limits how much irradiance can be used in occupied spaces.[1]

This means that achieving uniform and reliable surface disinfection in complex environments, while staying within exposure limits, can be challenging. Higher doses that may be effective against more persistent contamination or biofilms are typically not compatible with routine human occupancy.

Many far-UVC systems use broadband excimer lamps that emit a wider ultraviolet spectrum before filtering. The effectiveness and safety of these systems therefore depend on the quality and stability of the optical filters, which must reliably block longer, more penetrating UVC wavelengths throughout the lamp’s lifetime.

Degradation or misalignment of these filters can result in unintended emission of conventional UVC, potentially increasing material damage or exposure risks if not regularly monitored and maintained.

Spectral Blue MWHI® operates in the visible range (405 nm + 450 nm). When used as intended, this light does not cause photochemical damage to skin or eyes and is not restricted by the same type of occupational exposure limits as UVC. As a form of antimicrobial blue light (aBL), it can be applied in longer cycles and more flexibly integrated into daily hygiene concepts.

Penetration and Coverage in Real Environments

In practical room installations, far-UVC at 222 nm provides only limited irradiance and acts mainly within the direct beam path. Studies and engineering assessments, such as the Fraunhofer IOSB-AST white paper on far-UVC potentials and weaknesses, note that only directly illuminated areas receive an effective dose, while shadowed surfaces remain largely untreated. Because reflections from typical indoor materials are weak at this wavelength, far-UVC disinfection tends to be most efficient in line-of-sight configurations and at relatively short distances from the source.[2]

- In production areas and cleanrooms, where installations include equipment, piping, conveyors and shielded corners, some surfaces may receive limited dose from ceiling-mounted or fixed far-UVC sources.

Visible blue light has the ability to reflect and scatter efficiently from many technical surfaces, which can contribute to a more uniform distribution of light in a room. The Multi-Wavelength High-Intensity (MWHI®) approach used in Spectral Blue combines 405 nm and 450 nm wavelengths to enhance antimicrobial activity on exposed surfaces. This concept is capable of supporting coverage even in areas where direct line-of-sight is limited, while remaining compatible with sensitive environments.

Material Compatibility and Ozone

UVC radiation, including far-UVC, is known to cause gradual ageing of certain polymers, seals, adhesives and coatings. Extensive studies of polymer materials show that exposure to ultraviolet radiation leads to photo-oxidative degradation, loss of mechanical strength and alteration of material properties over time.[3, 4] 

- The degree of impact depends on dose, material type and exposure time, but in regulated production environments this is an important consideration. In addition, excimer-based UVC lamps may generate trace ozone if not properly filtered or if filters deteriorate, which requires appropriate design and monitoring.

Antimicrobial blue light (aBL) as used in Spectral Blue MWHI® is non-ionising and generally compatible with stainless steel, plastics and electronic components commonly found in cleanrooms and food-processing facilities. It does not produce ozone or similar by-products. This allows frequent or continuous operation without introducing additional chemical or material concerns.

How Antimicrobial Blue Light Works

Far-UVC inactivates microorganisms mainly by directly damaging their nucleic acids and structural proteins. This mechanism is efficient for airborne microorganisms and for surfaces that are directly irradiated, but its effectiveness can be reduced in shadowed areas or within thicker biological layers.

Antimicrobial blue light (aBL) acts through a different mechanism. Many microorganisms contain endogenous molecules such as porphyrins and flavins that absorb blue light. When excited, these molecules can generate reactive oxygen species (ROS), which then damage cellular components including membranes, proteins and nucleic acids.

This ROS-based pathway provides a broad antimicrobial effect against bacteria, yeasts and moulds. It has also been shown to affect biofilms and stress-tolerant populations in various experimental settings. Because the mechanism is oxidative and multi-target, the potential for classical resistance development is considered lower than for some single-target approaches. In practical use, continuous or repeated aBL exposure can help to maintain a lower microbial baseline between manual cleaning and disinfection cycles.

Research on far-UVC and biofilms indicates that 222 nm irradiation can damage or inhibit biofilms under controlled, close-range conditions. At the same time, published data from ceiling-mounted or room-scale installations operating within current exposure limits mainly demonstrate reductions in general surface contamination and airborne counts, rather than complete removal of mature industrial biofilms. This suggests that far-UVC is well suited for reducing airborne and freshly deposited microorganisms, while persistent biofilms on complex surfaces may require alternative or additional measures.

Maintenance and Operational Aspects

Far-UVC systems are based on krypton-chloride excimer lamp technology. Their lifetime and stability depend on the specific design, operating conditions and filter systems, and regular checks of output and filter integrity are recommended to ensure consistent performance and safety. Independent assessments, such as the Fraunhofer IOSB-AST white paper, have also noted that current far-UVC devices are relatively energy-inefficient. The low radiant power of these lamps means that achieving sufficient doses for full-room disinfection requires long exposure times, which limits their practicality for rapid or large-area applications compared with conventional 254 nm UVC or visible-light systems.[2]

When factors such as equipment cost, lamp lifespan and the remaining uncertainties about long-term ocular safety are also considered, far-UVC may be less suited as a general-purpose disinfection method.

Spectral Blue MWHI® uses LED technology with typical lifetimes up to 50 000 hours. There are no gas fills, mercury or optical safety filters as in excimer lamps, which simplifies maintenance and supports integration into automated night-time, off-shift or continuous disinfection programs.

Beyond Industrial Hygiene

The primary focus of antimicrobial blue light (aBL) in the Spectral Blue MWHI® concept is on GMP cleanrooms, laboratories and food-production environments. At the same time, the underlying safety profile also makes this type of technology of interest for healthcare and dental settings, where continuous background disinfection can complement manual cleaning and ventilation.

Comparison: Far-UVC vs. Multi-Wavelength Antimicrobial Blue Light (aBL)

Feature	Far-UVC (≈ 222 nm)	Multi-Wavelength Antimicrobial Blue Light (aBL) - Spectral Blue MWHI®
Spectral range	Ultraviolet-C (germicidal region)	Visible blue light (405 nm + 450 nm)
Primary mechanism	Damage to RNA/DNA and proteins through direct photochemical absorption	ROS generation via endogenous photosensitisers
Safety for operators	Subject to strict exposure limits; requires validated filters and monitoring	No comparable UVC-type exposure limits when used as intended; can be managed with standard lighting controls for comfort
Material compatibility	Possible long-term degradation of some plastics, seals and coatings	Generally compatible with common cleanroom, laboratory and food-contact materials
Ozone formation	Possible if not properly filtered or if filters deteriorate	None
Penetration and shadow areas	Most effective in direct line-of-sight; reduced effect in shaded or distant areas	Efficient reflection and scattering can support coverage in complex geometries
Biofilm considerations	Experimental effects at close range; limited evidence for removal of mature biofilms from ceiling-mounted systems at safe doses	ROS-based mechanism shown to affect biofilms in various studies; intended for routine surface hygiene support
Light source and lifespan	Excimer lamps, ca. 3 000 - 10 000 hours; lifetime and performance dependent on design and filters	LED modules, up to 50 000 hours
Maintenance requirements	Requires output and filter integrity checks; lamp replacement over time	Minimal maintenance; no filters or gas-filled lamps
Typical use areas	Airborne pathogen reduction and specific high-risk zones in occupied spaces	Surface and room hygiene in GMP cleanrooms, laboratories, food production and healthcare support areas
Typical application mode	Continuous or duty-cycled airborne disinfection within exposure limits	Continuous or scheduled operation alongside routine cleaning and disinfection

The Bottom Line

Far-UVC has a documented role in airborne pathogen control, especially in well-defined volumes where line-of-sight can be maintained and exposure limits are respected. It remains one useful tool in the broader infection prevention toolbox.

In many modern GMP, laboratory and food-processing environments, the main concerns are long-term contamination sources such as biofilms and complex surface structures. For these challenges, Multi-Wavelength Antimicrobial Blue Light (aBL) as implemented in Spectral Blue MWHI® provides a technically suitable option that can be integrated into daily operations without introducing additional chemical or UVC-related constraints.

Current evidence suggests that ceiling-mounted far-UVC systems are effective for reducing airborne and general surface contamination, but there is limited published data showing removal of mature biofilms at exposure levels acceptable for occupied spaces. Antimicrobial blue light offers a complementary approach aimed at continuous reduction of microbial load on surfaces, supporting existing cleaning and disinfection practices.

When selecting technologies, each facility should consider its predominant risks - airborne transmission, surface contamination, biofilms, material sensitivity and regulatory requirements - and choose a combination of measures that is both scientifically supported and practical for long-term use.

Sources

1. ICNIRP, Guidelines on Limits of Exposure to Ultraviolet Radiation of Wavelengths between 180 nm and 400 nm (Incoherent Optical Radiation), Health Physics 87(2):171–186 (2004)
2. Fraunhofer IOSB-AST, “Far-UVC – potentials and weaknesses” (white paper)
3. Maraveas, C. (2024) The Aging of Polymers under Electromagnetic Radiation. Polymers 16(5):689. DOI:10.3390/polym16050689.
4. Andrady, A.L., Heikkilä, A.M., Pandey, K.K. et al. (2023) Effects of UV radiation on natural and synthetic materials. Photochem Photobiol Sci 22:1177–1202. DOI:10.1007/s43630-023-00377-6.

Further reading

• Major sources of contamination in cleanrooms
• Blue light eliminates biofilms efficiently
• Substantial reduction of biofilms in a cleanroom: a Spectral Blue case study
• Safety profile of Spectral Blue
• How does blue light disinfection work?
• UV radiation and blue light disinfection - what are their differences?
• Blue light as a complementary strategy for chemical disinfection