The COVID-19 pandemic generated interest in applying germicidal ultraviolet (GUV) lamps in buildings such as healthcare facilities. Traditionally used in applications such as water treatment, industrial processes and ventilation, these lamps irradiate air or surfaces to neutralize pathogens such as SARS-CoV-2, which causes COVID-19.

Manufacturers have developed products based on a range of approaches. According to Research and Markets, the global GUV market was valued at $335 million in 2020 and is projected to grow to $682.9 million in 2026, primarily based on increased demand for products used for air disinfection.

Education and safety risks

On the electromagnetic spectrum, the UV range constitutes wavelengths from 100–400 nm, with UV-C (100–280 nm) being most effective against pathogens and preferred for GUV applications. The primary challenge is safety, as UV-C radiation poses serious risks to human eyes and skin and is also harmful to plants, paints and organic materials. The name “germicidal lighting” is a misnomer because it should only be used for disinfection, not illumination.

When evaluating solutions, ECs should be cautious and educate themselves. What are the characteristics of the application, and what does the owner need? What pathogens does the considered GUV source neutralize, where does disinfection occur and how quickly are pathogens neutralized?

As there are few accepted standards for this equipment, what is the manufacturer’s reputation, what evidence do they offer to support their product, and what features and fail-safes do their products offer to safeguard users? Does the product meet NIOSH, UL, IEEE, IES and related safety standards? What is needed for safe installation and operation? What commissioning and maintenance are required?

The Illuminating Engineering Society recently published a recommended practice for lighting professionals interested in applying GUV for disinfection. ANSI/IES RP-44-21, “Ultraviolet Germicidal Irradiation (UVGI),” covers applications, technologies, risks, safety measures and precautions, as well as commissioning and maintenance considerations.

RP-44 identifies common GUV lamps as low-pressure mercury (predominantly 254 nm), excimer lamps (mostly 222 nm, which, if operated in accordance with photobiological safety limits, may reduce adverse effects on human skin and eyes), and UV-C LEDs, which are still developing.

Preventing exposure

Because of the safety risks, UV-C radiation is typically applied so that exposure to people, animals, plants and sensitive materials is prevented. This means applying GUV radiation to a part of the room while it is occupied (such as above occupants’ heads if the ceiling is of sufficient height) or applying it while the room is unoccupied.

Three primary approaches facilitate GUV disinfection in buildings:

• Air purification disinfects air circulating through air handlers, air purification devices and the upper-room space cavity.

• Direct UV-C irradiation is provided by luminaires and portable devices that disinfect air and surfaces within line of sight, deployed in rooms when unoccupied.

• A hybrid of the two, such as luminaires that disinfect upper-room air when the room is occupied and then disinfect air and exposed surfaces in the space below using direct emitters when it is unoccupied.

More specifically, applications include in-duct, upper-room, whole-room and mobile (e.g., robotic) systems, in addition to handheld and air-cleaning devices. In-duct products are installed in HVAC air handlers and ducts to provide air and surface disinfection. Upper-room systems use GUV lamps that irradiate the air above 7 or more feet, ideally paired with ventilation that constantly mixes the room air. Whole-room systems irradiate air and surfaces in the line of sight and require safety measures to avoid exposure for humans lacking PPE.

Mobile systems such as robots can be used to disinfect surfaces (and much of the air, depending on circulation) when the room is unoccupied. For more thorough surface disinfection—either not reached by an upper-room system or not within line of sight for a whole-room system—additional measures such as manual cleaning can be added for a multibarrier solution.

For air disinfection, RP-44 states that upper-room systems remain the safest, most effective UV-C application. The main advantage is that disinfection takes place in the same room where pathogen transmission risk is greatest. The main disadvantage is the requirement for a sufficient ceiling height, and occupants may be uncomfortable sharing a room with an active GUV system. For whole-room disinfection, suspended devices directing UV-C radiation downward or mobile systems can be used, if strict safety precautions are taken to avoid human exposure.

GUV products should be installed with strict adherence to manufacturer instructions and applicable safety measures and standards. Depending on the GUV approach, sophisticated commissioning, maintenance and routine inspection may be required, which necessitate retention of system documentation, training and proper equipment such as calibrated meters.