NIST upgrades its UV calibration service for U.S. test clients

24 Jul 2024

Previously, the dedicated lab was not optimized for critical UVC wavelength ranges for disinfection.

The auto-sized unit is the heart of NIST’s new UV Spectral Comparator Facility.

Ultraviolet light has many applications from disinfecting our hospitals, to killing pathogens in drinking water, even curing newly-applied nail polish, and. But how can we be sure it’s being used in ways that are safe and effective?

To understand this, the U.S. National Institute of Standards and Technology (NIST) has rebuilt its specialized calibration laboratory, called the Ultraviolet Spectral Comparator Facility (UVSCF), where NIST’s industry customers send their UV detection equipment to be precisely measured and calibrated.

UV light serves a wide variety of applications. The germicidal properties of UV light make it a valuable tool for sanitization and disinfection, especially in health-care settings. It also is an effective way to combat microbial contamination in water and is used for drinking water, wastewater and surface water disinfection.

Homeowners use UV-cured epoxy to put new kitchen countertops in place. In the nail salon industry, UV light boxes cure gel nail products. And, in recent years, a proliferation of new consumer products, such as UV-protective clothing, prevent unwanted exposure to UV light. Carefully calibrated UV light sources are needed to ensure that these products work as intended.

UV spectrum

There are three different categories of UV light based on the wavelength: UVA, UVB and UVC. While NIST's new calibration system caters to all three, its focus is on accurately measuring UVC light, which falls into the 200 nm - 300 nm range. UVC light has shorter, higher-energy wavelengths compared with UVA and UVB, which makes UVC highly effective at killing bacteria and viruses.

NIST research chemist Cameron Miller commented, “Approximately 100,000 people a year die from health care-associated infections in the U.S. They go into a hospital to be treated for one thing, but then end up with an infection from inadequate sanitization Using UV light to disinfect rooms and equipment offers a potential solution.”

However, UVC light can also harm human skin and eyes, so it needs to be used carefully. Organizations that use UV light, from the military and research institutions to universities and industrial manufacturers, can verify that their UV light sources are emitting the right amount and intensity of light with a compact, hand-held device called a UV detector.

Such detectors need to be calibrated, so users periodically send them to NIST’s Ultraviolet Spectral Comparator Facility. There, the NIST experts calibrate the detectors by exposing them to specific UV wavelengths and comparing their readings to a precisely calibrated standard detector.

“We can measure UV light at short wavelengths with extremely high accuracy and precision,” said NIST physicist Jeanne Houston. “The UVC range of the UV spectrum is the most challenging part to measure, so achieving this level of precision is something we don’t typically see in this field.”

NIST has maintained a UV calibration facility since the late 1980s. However, by the mid-2010s, the facility could no longer meet the needs of emerging technologies such as UV disinfection because it was not optimized for the critical wavelength range needed for disinfection. The Covid-19 pandemic brought a new interest in improving and rebuilding the system.

“Once Covid struck, UV disinfection was hitting the big time and we were able to totally rebuild the system,” said Houston. “We have implemented massive improvements, and it is my opinion that our new facility is the best in the world.”