Upper room germicidal UV (GUV) is recognized by the World Health Organization (WHO) and the US Center for Disease Control (CDC) as an important environmental control to reduce TB transmission, especially in high risk, low- to middle-income settings where natural ventilation is unreliable, seasonal, or ineffective and where mechanical ventilation is absent or limited, which is most places. It is especially difficult to achieve good ventilation within hospital wards unless they are designed for natural ventilation, and outdoor conditions are optimal.
Evidenced-based research shows that upper room GUV fixtures with good air-mixing placed in an actual TB ward in South Africa reduced TB transmission by ~80% (Mphaphlele 2015). Similarly, in Peru, TB transmission was reduced by 73% (Escombe 2009). The Mphaphlele study is being used as a basis for new international dosing guidelines for GUV and will be the basis for a global implementation strategy supported by USAID and other sources.
How Does Upper Room Germicidal UV work?
Germicidal UV (254 nm) readily inactivates most airborne pathogens. The dose required for inactivation depends on the organism, with viruses (no cell wall) generally easier to kill than fungal spores, and Mycobacterium tuberculosis in-between, but readily inactivated. Room occupants are not harmed when properly designed fixtures are installed appropriately in the upper room and tested before use. (Note that this is not UV in room air cleaners, mechanical air moving devices that rarely move enough air to effectively achieve the recommended 6 to 12 equivalent room air changes per hour required for good air disinfection.)
How is GUV applied?
A TB transmission risk assessment identifies high risk areas in health care facilities, e.g. an emergency department, OPD or X-Ray room for GUV treatment. Dimensions of these rooms and spaces are taken to determine if there is enough upper room height to place the GUV fixtures safely. Dosing (numbers and power of fixtures per cubic meter of room volume) is based on the total fixture UV output. An example of a recent application of germicidal UV, natural ventilation and air-mixing is shown here – the new Butaro Cancer Treatment Center by Mass Design. The other important component of upper room GUV air disinfection is good air mixing, easily achieved by inexpensive, low-tech, low velocity ceiling fans. The combination of ceiling fans and adequate upper room GUV assures effective air disinfection equivalent in many settings to 10 to 20 room air changes per hour.
How is occupant safety assured?
Occupant safety is assured through a commissioning process – a review of the GUV fixture installation and measurements of eye level UV irradiance standing, seated or on patient level taken before the fixtures are turned on for fulltime use. In-service staff training with installation of appropriate multilingual signage allows opportunity for staff questions about benefits and safety.
What are the costs, and is upper room GUV cost effective?
Typically, GUV fixtures should last 15 years, with an occasional need to change an electronic ballast. Fixture costs in volume could be in the $500 range, depending on the source, but installation and wiring costs can double that initial expense. The ongoing costs include supplying lamps for annual re-lamping, and regular cleaning and re-measurement for output and safety. A UVC meter for measurements is needed, as are cleaning supplies. The electrical cost per fixture is the same as running an energy efficient fluorescent light. A generator is needed in areas with unreliable electricity. Specific numbers of fixtures and related costs need to be refined based on local conditions. Although more expensive than natural ventilation, where needed, upper room GUV is nearly 10 times more cost-effective than mechanical ventilation or any tested room air cleaner system.