“It’s changed the paradigm on disease transmission,” said Julien Renaud, scientific liaison with Sanuvox Technologies. “There's a lot more focus and understanding that a lot of diseases are actually transmitted the airborne route, especially respiratory diseases.”

This increases the need for additional methods to control things like HAIs (healthcare-associated infections), and with the focus on airborne transmission, HVAC takes center stage.

Enter: UV-C.

UV-C Breakdown

Ultraviolet germicidal irradiation (UVGI) employs UV-C (ultraviolet light) to immobilize the DNA of bacteria, viruses, or microorganisms, stopping their spread.

“For nearly a century, scientists have known that the UV-C wavelength alters microbial DNA in bacteria and fungi and RNA in viruses, rendering pathogens inactive and unable to replicate,” said Joe Kalman, sales director for UV Resources and Steril-Aire. “Moreover, this germicidal process occurs without creating hazardous chemicals, VOCs, or dangerous byproducts.”

Not to mention that UVGI has already been extensively peer-reviewed and studied since its inception, and has been recognized in two ASHRAE Handbook Chapters.

As far as how germicidal UV-C works, it’s actually pretty straightforward.

“Germicidal UV-C is essentially the same physical principle as visible light … it's all what we call the electromagnetic spectrum,” Renaud said. “So essentially, it's photons — the same kind of particle that transmits the visible light — but instead, it's on shorter wavelengths than visible light. So we're talking more about the 254-nanometer range of wavelength instead of 400 to 700 (which is the visible light that we see with our eyes), and what people realize is that essentially between 250 and 265 nanometers of wavelength is the optimal absorption wavelength of nucleic acids.”

By bombarding DNA or RNA molecules in a virus or bacterium with enough UV radiation, “we're able to change and break down the DNA, which essentially prevents them from reproducing and, all in all, sterilizes them,” Renaud said.

UVGI employs UV-C to deactivate that DNA of things like bacteria or viruses, or other pathogens or microorganisms that could multiply and cause disease.

“UV-C also complements other engineering controls designed to mitigate disease transmission,” Kalman said. “ASHRAE and public health agencies recommend a multilayered approach incorporating several infection-control measures, such as UV-C disinfection, to help ensure that whatever pathogen cannot be removed by one method (say filtering or cleaning) is inactivated by another (UV-C).”

Changing the Paradigm

UV-C’s popularity in the healthcare sector comes not only from its disinfecting capabilities, but also because of its cost-effectiveness and ease of installation — even when retrofitting into an existing central HVAC system.

“Healthcare facility professionals and infection preventionists can utilize germicidal-UV technologies to assist in mitigating concentrations of pathogens in a highly reliable and cost-effective fashion,” Kalman said. “All healthcare facilities wage a three-pronged war against diseases, combatting the spread of hospital-acquired infections, antimicrobial-resistant threats, and emerging diseases. … UV-C can be installed inexpensively throughout health care facilities by using upper-room units for interior spaces; lamp fixtures for HVAC ducts for airstream inactivation; and in air handling units to disinfect airstreams, coils, and other potential reservoirs for microbial growth and proliferation.”

Click graphic to enlarge

UV-C ENERGY: Upper-room germicidal fixtures are wall-mounted near a room’s ceiling and use baffles to direct the UV-C energy upward and outward, ensuring that no UV-C energy enters the occupied portion of the room. (Courtesy of UV Resources and Steril-Aire)

In some regions, legislation is driving the focus on HVAC systems in health care as well.

“In Canada, there's more focus on additional methods of hospital-acquired infection prevention because of changes in regulatory setting with the new standard norm CSA Z8000 [for Canadian Health Care Facilities], which says that new engineered measure of the disease prevention should be applied to all new and existing renovation for hospital and other healthcare settings,” Renaud said.

Other IAQ solutions gaining traction in the HVAC/health care space include purification, ventilation, and filtration — specifically, through the use of HEPA filters, which Renaud called “the gold standard” in terms of filtration. The thought process is that these solutions, working in tandem, provide layers of protection in indoor air safety, minimizing the risk of airborne transmission in healthcare facilities as well as providing better IAQ.

“UV-C supplements infection-control protocols for disinfection, sterilization, and manual cleaning in healthcare settings such as ER waiting rooms, intensive care units, operating theaters, urgent care clinics, doctor and dental offices, nursing homes, and extended care facilities,” Kalman said.

In addition to immobilizing infectious pathogens 24 hours, seven days a week, Kalman said UV-C systems provide some level of protection when staff don’t, or can’t, follow mitigation protocols, or if emerging diseases sidestep existing protocols, or when HVAC or room-pressurization systems are compromised.

“The market is starting to view UV-C as air filtration,” Kalman said. “Every application works better and longer, and users are happier when UV-C is installed in air handlers.”

A Brighter Future

In the last decade, UV-C installation has really become the standard in the healthcare sector, given its ability to be easily retrofitted, save money and energy, and inactivate those infection-causing microorganisms on HVAC surfaces and airstreams. As the technology continues to adapt, maximizing its potential becomes that much simpler.

AIRBORNE: The GLO UV-C disinfection upper-room fixture series from UV Resources inactivates airborne pathogens at their source in seconds from people coughing, sneezing, or talking. (Courtesy of UV Resources and Steril-Aire)

“In particular, predictive modeling and efficacy software are now best practices for determining the specific UV-C dose/fluence required to inactivate particular viruses and bacteria,” Kalman said. “Many factors influence the sizing of UV-C airstream disinfection systems, and there is no one-size-fits-all scenario.”

Looking ahead, Renaud feels the HVAC industry would benefit from standardization for UV-C products. It’s difficult to validate UV-C technology in the field, he said, meaning it’s instead normally validated by extensive data collected on various factors such as how much UV-C light is used, the wavelengths, and how long UV-C exposure lasts. The downside of this is that unethical salespeople could sell LED lights, claiming they emit UV-C disinfection, without the customer ever knowing otherwise.

“In the IAQ field at large… it's still pretty much the Wild West when it comes to biological contaminants,” he said. “A lot of people are free to claim whatever they want regarding their technology — even when it comes to UV disinfection.”

Water has been treated by UV disinfection for the past 100 years, he continued, “but when it comes to disinfecting the air, there's a lot of systems out there that don't have enough power, that are not well-optimized, or validated.

“People are not well-versed on how it works, and that leads to a lot of false or non-effective products out there,” Renaud said. “We would gain a lot by having standards put in place, and those are coming. … Hopefully, the future will be brighter under UV lights.”