Germicidal UV FAQs

Frequently Asked Questions

Infection Control

Can UV-C Inactivate the virus that causes COVID-19?

Researchers now know that the 254 nm germicidal wavelength can inactivate the genetic material in the SARS-CoV-2 virus [i]. Moreover, when aerosolized the COVID-19 causing virus is likely to be more susceptible to UV-C damage than other coronaviruses such as SARS-CoV-1 (that led to the 2003 severe acute respiratory syndrome) or MERS-CoV2 [ii] (that caused the 2012 Middle East respiratory syndrome).

It is important to note that science has not found any microorganism that can withstand the destructive effects of the UV-C germicidal wavelength, including superbugs and other antibiotic-resistant germs. In fact, viruses and bacteria cannot develop a resistance to germicidal UV because it uses energy to kill, rather than synthetic or chemical elements. Today, there are several approaches to using this decades-old technology to reduce microbes in the air and on surfaces, including airstream disinfection (also known as in-duct) and upper-room decontamination.

Germicidal UV-C air disinfection systems are installed in a building’s HVAC ductwork to disinfect moving airstreams before they reach employees. Kill ratios over 99 percent on a first-pass basis have been demonstrated by the Environmental Protection Agency (EPA) and the National Homeland Security Research Center. As air is re-circulated, concentrations of infectious pathogens are further reduced by each subsequent pass (“multiple dosing”).

Upper-room UV-C is the oldest disinfection application of the germicidal wavelength for airborne inactivation and is recommended for improved control of highly contagious airborne diseases such as Tuberculosis by the U.S. Centers for Disease Control and Prevention and the National Institute for Occupational Safety and Health.

[i] National Academies of Sciences, Engineering and Medicine. Does ultraviolet light kill the coronavirus? October 2020. Retrieved from

[ii] Environmental Protection Agency and National Homeland Security Research Center. Biological Inactivation Efficiency of HVAC In-Duct Ultraviolet Devices. Technical Brief. Washington, DC: EPA;2006. (EPA/600/S-06/034). Retrieved from

How effective are each at getting rid of coronavirus?

Scientists know that coronaviruses are transmitted via air and direct contact [iii]. At the same time, research has shown that exposure to the UV-C waveform (253.7 nm) is a practical and cost-effective method of inactivating airborne viruses, mycoplasma, bacteria, and fungi on clean surfaces. [iv]

Because of the extended incubation period for some of these diseases, people can spread the virus before anyone knows they are contagious and, more importantly, before anyone can take precautions. Therefore, it is incumbent on facility managers to use preventative infection control measures such as germicidal UV-C to mitigate the potential spread of airborne diseases.

[iii] Kowalski, W. (2015). SARS Coronavirus UV Susceptibility. Retrieved from

[iv] Department of the Army. (2009) Safety standards for microbiological and biomedical laboratories. Retrieved from

Can viruses spread through HVAC ducts?

Because most viruses can be transmitted via air and direct contact, it could be presumed that HVAC systems can inadvertently broadcast the infection, increasing its spread. Therefore, facility managers should consider employing both upper-room UVGI and HVAC germicidal fixtures to ensure the greatest mitigation practical for control of microbes and airborne microorganisms in communal spaces.

Airborne droplets containing infectious agents can remain in room air for 6 minutes and longer. Upper-room UV-C fixtures can destroy those microbes when they are exposed to the UV-C energy in a matter of seconds. Kill ratios up to 99.9 percent on a first-pass basis have been modeled and, as air is recirculated, concentrations are further reduced by each subsequent pass (“multiple dosing”).

Surface-cleaning UV-C systems provide 24/7 irradiation of HVAC/R components to destroy bacteria, viruses and mold that settle and proliferate on HVAC coils, air filters, ducts and drain pans. UV-C prevents these areas from becoming microbial reservoirs for pathogen growth that can eventually become airborne and circulated by HVAC systems.

A system installed for HVAC surface irradiation, while not specifically designed for it, can also provide first-pass kill ratios of airborne pathogens of up to 30 percent, along with the primary benefits of restored cleanliness, heat-exchange efficiency and energy use.


Do UV-C lamps produce ozone?

While the Ultraviolet spectrum contains four separate wavelengths—UV-A, B, C and Vacuum UV—each operates at different energy levels and only one is capable of producing ozone (Vacuum UV).

As you’ll note in the graphic below, Vacuum UV operates in the 100-200 nm range, where it is capable of producing ozone. UV-C, conversely, reaches its optimal germicidal strength near 253.7 nm. Because ozone may only be produced below 200 nm, at 253.7 nm (rounded to 254 nm), the germicidal wavelength does not generate ozone.

In addition to the stronger 254 nm wavelength that does not produce ozone, UV-C lamps offer another layer of ozone protection.

Most germicidal lamps, including those from UV Resources, are produced with doped quartz glass, which blocks the transmission of the 185 nm ozone-producing wavelength. The doped quartz glass allows the 253.7 nm radiation to pass through, but it blocks the 185 nm wavelength from escaping. Therefore, germicidal lamps with doped glass CANNOT produce ozone. Learn why UV-C cannot produce ozone.

Does UV-C replace filters?

No, a UV-C fixture is an air conditioning component that is in addition to other system parts. These include the coil, heating core, fan, dampers, humidifiers, filters, etc. All are designed to do some form of work within the air handler a UV-C fixture is just one of these components.

While antibacterial UV-C applications have improved indoor air quality for decades, it was the COVID-19 pandemic that took the technology’s use in the eyes of building managers from energy savings to infection mitigation. Just as no one would operate an HVAC system without air filters—the time is near when no one will operate HVAC/R systems without UV-C installed.


Where are the best locations in a commercial space to add UV-C fixtures?

The selection of an air or surface disinfection system is based entirely on the application.

Upper-Room/Air Decontamination Systems

Purpose: Designed to mitigate the spread of infectious diseases in high traffic, communal areas that are ideal for cross-contamination.

Rationale: Because people can be infectious before they are symptomatic, a significant value of UV-C technology is the ability to limit the spread of contagious diseases and bacteria 24/7/365.


  • Offices/call centers
  • Doctor/dentist offices
  • Lecture halls & classrooms
  • Sporting arenas
  • Meat/dairy processing
  • Emergency shelters


HVAC Airstream-Disinfection Systems

Purpose: Designed to inactivate microorganisms and disinfect moving airstreams “on-the-fly.”

Rationale: Established means of killing airborne pathogens and mitigating the spread of infectious diseases in ventilation systems, as well as in occupied spaces.


  • HVAC Plenums
  • HVAC Ductwork
  • Variable air volume/Mixing boxes


Coil/Surface-Irradiation Systems

Purpose: Designed to destroy bacteria, viruses and mold that proliferate on HVAC coils, air filters and ducts.

Rationale: UV-C removes the biofilm that grows on cooling coil surfaces and improves heat-transfer efficiency and lowers HVAC energy use.

Application: Any building with a HVAC system (stationary AHU, rooftop systems, or individual fan coil units).

How do you size UV-C applications?

For IAQ, improved heat transfer, reduced maintenance and odor, an approach used for well over ten years is to put the lamp row centerlines on 30-inch to 45-inch centerlines. Most highly regarded manufacturers have software that can size these types of installations, and more. Only consult one of these reputable manufacturers when sizing infectious disease agent applications.

Is UV-C hard to install?

Not at all. Simple installation instructions are provided along with layout drawings populated with all the necessary dimensional specifics. Product designs are emerging that allow installation of UV-C in AHU’s in under an hour in many cases. This also includes fan-coil, unitary and rooftop units, the hardest systems to keep clean. Consult a reputable factory and then involve them in any infectious disease application.


How do you dispose of used lamps?

Currently, most users would dispose of them as they would any glass trash, such as their fluorescent lamps. Large fluorescent lamp users follow EPA and state guidelines, and UV-C lamps would then fall into those same guidelines. If you have a fluorescent lamp disposal program in place, UV-C lamps would simply fall into that same program.

When do you change lamps?

For infectious disease applications, change-out should be performed using an output measurement device such as a radiometer, while following factory specifications and/or recommendations. For IAQ or mold control, large installs might benefit from a radiometer to preclude premature change-outs. Changing lamps when their output decreases by 20 percent are common, this usually occurs in about 12-15 months. So for installs with no radiometer, re-lamp at least annually and replace burn-out as soon as possible.


What is UV-C?

UV light comprises a segment of the electromagnetic spectrum between 100 and 400 nm, corresponding to photon energies from 3 to 124 eV. The UV segment has four wavelengths, labeled: UV-A (400 to 315 nm); UV-B (315 to 280 nm); very high energy and destructive UV-C (280 to 200 nm); and vacuum UV (200 to 100 nm).

UV-C’s germicidal or germ-killing effects are well proven. The 253.7 nm electromagnetic waveform is well absorbed by DNA and RNA (the genetic code for all lifeforms), changing its structure. This damage inhibits the ability of the affected cells to reproduce, meaning that they cannot infect and are no longer dangerous.

Is UV-C harmful?

We’re exposed to parts of the UV spectrum while outdoors. Generally, excessive UV exposure can produce adverse effects depending on wavelength, type and duration, and UV response differences between individuals. The three basic wavelengths:

— UV-C – includes the germicidal wavelength of 253.7nm and is used for air and water disinfection. Human overexposure causes temporary skin redness and harsh eye irritation, but no permanent damage, skin cancer, or cataracts.
— UV-B – is a narrower but more dangerous band of UV. Prolonged exposure has been associated with skin cancer, skin aging, and cataracts (clouding of the lens of the eye).
— UV-A – is more predominant outdoors than the other two. It helps to tan our skin and is used in medicine to treat certain skin disorders. It is generally a harmless wavelength.

UV-A, B and C will damage collagen fibers and accelerate skin aging. Generally, UV-A is the least harmful; UV-B contributes to DNA damage and cancer. It penetrates deeply but does not cause sunburn. Because of no reddening (erythema) it cannot be measured in SPF testing. There is no good clinical measurement of UV-B blocking, but it is important that sunscreens block both UV-A and B. UV-C however, penetrates superficially and has not been associated with long term tissue effects.

How does it affect germs?

Microorganisms are simple organic structures that readily absorb the UV-C wavelength, causing photo-disassociation (destruction). A microbe’s DNA (deoxyribonucleic acid, is first to be adversely affected due to its weaker molecular bonds. In hundredths of a second, it suffers irreparable damage. The subsequent loss of genetic instructions causes cell death and/or the inability to replicate, rendering them harmless. Continuous exposure causes uninterrupted degradation, such as the sun does, only significantly faster.

Can UV-C save energy?

Yes, in literally thousands of controlled tests, organic materials build-up on coils was removed with UV-C to provide two eventual results: 1. the pressure drop across a coil declines to increase air flow. 2. the leaving air wet-bulb temperature differential increases. Energy savings are therefore through increased heat absorption (transfer), reduced air horsepower (or increased air volume) and/or reduced run time, including at a condenser. These reductions and increases always manifest themselves in some form of energy-saving work.


Does UV-C kill microbial growth and pathogens?

The CDC [v] and ASHRAE have recommended UV-C as one technology that can “reduce the risk of dissemination of infectious aerosols in buildings and transportation environments.” [vi] ASHRAE has recognized that the 253.7 nm germicidal C-band wavelength inactivates virtually all microorganisms living on HVAC/R surfaces with a kill ratio of 90 percent or higher, depending on UV-C intensity, length of exposure, lamp placement and lamp life cycle. In fact, a CDC-funded study conducted in two hospitals found that UV-C reduced the total number of colony-forming units of any pathogen in a room by 91 percent. [vii]

Science has yet to find a microorganism that is immune to the destructive effects of UV-C, including superbugs and all other antibiotic-resistant microbes associated with healthcare-associated infections.

[v] CDC. COVID-19 Employer Information for Office Buildings (September 11, 2020). Retrieved from

[vi] ASHRAE Position Document on Infectious Aerosols (April 14, 2020). Retrieved from

[vii] Anderson D. J., et. al. (2013) Decontamination of Targeted Pathogens from Patient Rooms Using an Automated Ultraviolet-C-Emitting Device.” Infection Control & Hospital Epidemiology. Retrieved from

Did You Know?

Fun Facts & Information About UV-C

  • Did you know that “bioaerosols account for a larger portion of the IAQ issue than any other single thing?” – Dr. Harriet Burge, HVAC industry scientific researcher.
  • Did you know that one would need a 5- hour daily exposure to UV-C for 300 years to potentially cause skin cancer? UV-B is most dangerous for carcinoma or melanoma.
  • Did you know that science has yet to find a microorganism that’s totally immune to the destructive effects of UV-C?
  • Did you know that it’s the Argon gas in a UV lamp that produces the color blue? It does this same thing in a bug zapping lamp to attract them.
  • Did you know that most mold and TB never die but rather go dormant? This is the main reason science wants the TB microbe exposed to UV-C, as it permanently destroys it.
  • Did you know that after a significant number of tests, researchers could always grow various microbes on the media of anti-microbially treated air filters?
  • Did you know that the hardest to kill microbe can be easily destroyed in less than one second by properly using the cheapest UV-C lamp available.
  • Did you know that “Battelle” was able to kill the hardest to kill Bacillus spore to 6- 9’s of efficiency in a moving airstream of 500 feet per minute! Anthrax is no problem.
  • Did you know that UV-C turns organic matter directly into gas and vapor by breaking chemical bonds and it does not produce heat while doing so?
  • Did you know that the angle of incident reflection from all but a perfectly polished surface, when struck with UV’s “¼” micron wavelength (“C”) is unpredictable?
  • Did you know that mold is at the bottom of the food chain so its process of digestion is referred to as being in the category of decay?
  • Did you know that microbes are truly ubiquitous? An identifiable microbe of some known type, in some form of “dormancy”, can be found most anywhere.
  • Did you know that UVC lamp mercury vaporizes in its low-pressure argon plasma to be struck by electrons; that produces the desirable 253.7nm germicidal photons.
  • Did you know that the mycotoxin called aflatoxin is from the mold Aspergillus flavus, and is some 1000 times more carcinogenic than the next most carcinogenic substance?