Do far ultraviolet-C light technologies increase ozone concentrations in healthcare facility patient rooms?

To the Editor -Ultraviolet-C (UV-C) light is effective for inactivation of pathogens in air and on surfaces. 1In recent years, far-UV-C light (200 to 230 nm) has been proposed as an alternative to 254 nm UV-C light that may provide similar efficacy while being safe in occupied areas. 2,3However, there is concern that far-UV-C light could have adverse health effects due to production of undesirable air byproducts, particularly ozone. 2,4Far UV-C light can generate ozone that may accumulate in indoor areas with suboptimal ventilation. [4][5]5][6][7][8] However, previous studies have not reported ozone concentrations in well-ventilated healthcare settings.Therefore, we examined the impact of a far UV-C technology on ozone concentrations in unoccupied hospital rooms.The evaluation was approved by the Cleveland VA Medical Center's Biosafety Committee.Testing was performed in June 2024.Three far UV-C technologies were tested in a non-ventilated room (32.4 m 3 ).The devices were turned on at 8 A.M. and off at 3 P.M. or 4 P.M..The devices included the Pathogen Suppression System (Mynatek, Inc., Oakland, California), 2 Visium 1 with diffused optics (Lit Thinking, Orlando, Florida), and a 250-Watt GermBuster Channel (Sterilray, Inc.). 9Each Pathogen Suppression System contains 3 Care222 Filtered Far UV-C Excimer Lamp Modules (Ushio America, Cypress, California); Visium 1 devices contain 1 Care222 module.Per the manufacturer, a single Visium 1 with diffused optics is certified as producing zero ozone emissions by Underwriters Laboratory 2998.As a positive control, we tested an electronic air cleaning device that produces hydroxyl radicals but also generates ozone.Based on the results in the non-ventilated room, the electronic air cleaner and Pathogen Suppression System were used for testing in a double-occupancy positive-pressure patient room (124.8 m 3 ) with 8 total air changes per hour and a minimum of 2 changes of outdoor air per hour; 2 of the devices (6 total Care222 modules) were operated because the manufacturer recommends use of 2 devices in patient rooms. 3The devices were turned on at 8 A.M. and off at 4 P.M.. Testing of the Pathogen Suppression System was also completed in a single-patient room (74.8 m 3 ) with the same air changes per hour.