Ultraviolet germicidal irradiation, also known as UVGI, is emerging as a proven technology in the fight to reduce healthcare-acquired infections (HAIs). In essence, UVGI technologies kill pathogens in the air and on surfaces by using UV-C light to scramble microorganisms’ DNA and prevent their reproduction.

The non-ozone-producing wavelength is the most effective wavelength for biological sterilization, and it is exceptionally effective at deactivating viruses, bacteria and mould. While some microorganisms may require longer exposure times, all can be sterilized by UV-C.

Given the efficacy of UVGI technology, it’s no surprise that engineering and maintenance departments in Canadian hospitals are using the technology to disinfect HVAC systems and surgery suites as they grapple with a growing health risk. An alarming one in nine patients acquires an infection while receiving hospital care, which amounts to 220,000 cases and 8,500 to 12,000 patient deaths annually, according to the Canadian Union of Public Employees (CUPE). CUPE also reports that HAIs are costing Canada’s healthcare network more than $1-billion annually.

Hospitals have been using UV for many years to sterilize equipment and surgical tools. They have also used wall-mounted UV fixtures designed as upper room air disinfection systems. Mobile “robots” and stationary ceiling lamps have more recently become popular choices for UV surface disinfection.

While UVGI’s main appeal in healthcare applications is HAI prevention, other benefits include reduced HVAC maintenance costs and increased energy efficiency. UVGI is also used in ice machines and water dispensers to sterilize unhealthy biological contaminants that can potentially be passed onto patients.

Using UV-C on HVAC coils

The dark, moist interiors of an HVAC system’s evaporator coil and inside walls offer an ideal environment for mould, mildew and other biological growths. These systems range from large rooftop packaged units to indoor air handlers or even two pipe/four pipe ventilation equipment typically located under patient room windows. The process of dehumidifying air conditioning wrings out airflow moisture, which condenses on coils, drain pans and other interiors, and nourishes microbes.

UV-C light systems lamps range from 32 to 64 inches long and are usually positioned a few inches from the intake side of the HVAC system’s coil, where they sterilize microbes 24 hours a day and discourage biological growth and accumulation. While typically positioned to target the coil, the residual UV-C light shines throughout the entire HVAC encasement and down to the drain pan, which are all potential microbial growth areas as well as possible source of pathogens that may blow into the facility.

Biological growth on coils, a health risk itself, also attracts dirt that clogs the coils. Every facility, especially hospitals, must clean HVAC coils periodically. Eliminating these hard-to-remove biological growths cuts coil cleaning time, chemical use and maintenance costs.

Besides reducing coil maintenance costs, another secondary UV-C benefit is energy efficiency. Lab tests, including a 2004 Purdue University study, have shown that the slightest of heat transfer-reducing biofilms can dramatically decrease HVAC coil energy efficiency. Furthermore, the added air resistance of biofilm on the coil fins can raise static pressure, which results in higher fan energy.

While the primary task of coil UV-C light systems is to disinfect surfaces inside the HVAC system, microbes in the airflow passing through the system are also disinfected as they come into contact with the UV-C field. This is especially effective in HVAC systems designed for re-circulating hospital return air, which may contain pathogens such as tuberculosis, influenza, VRE, MRSA and C. difficile. The UV-C field can even kill outdoor allergens brought into the HVAC system through the course of complying with code requirements for ventilation.

Airborne duct UV-C systems

Besides coil systems, there are also UV-C light systems designed for ductwork interiors. Unlike coil lamps, which are positioned perpendicular to the airflow, in-duct lamps are positioned parallel to the duct run, which gives pathogens a longer disinfection dwell time as they pass through the UV-C field. They are typically installed inside the return or supply side, although the former is more effective because slower air velocities result in a longer dwell time.

Surface disinfection

Even with the best terminal-cleaning practices, a patient or operating room can remain a potential source of harmful microorganisms, which may help explain the CUPE’s findings that MRSA increased 17-fold in Canadian hospitals between 1995 and 2006. However, maintenance budget cuts, high turnover rates, and poor training can all lead to incomplete surface cleaning. The UV industry’s answer has been UV-C lamps that disinfect surfaces, particularly in the critical environments of operating rooms.

In the last decade, two types of UV surface systems — robots and stationary ceiling systems — have become popular methods of disinfecting rooms during unoccupied hours, as they are the only two options on the market outside of manual labour. Mobile UV-C robots cost more and require skilled operators, but they don’t require installation, can be moved to nearly any unoccupied room, and may execute faster disinfection times. Stationary, automatically operated UV-C lamp systems do require installation, but cost less and are designed for total room coverage regardless of furniture and equipment positions.

New healthcare markets for UV-C

Although hospitals have used UV in different capacities since the 1920s, studies have only in the last few years, since the emerging popularity of robots, gauged its effectiveness in defending against HAI. A third-party indoor air cleaning device test lab, the Ireland-based Airmid Healthgroup (AHG), conducted one recent study, which found UV light to be “highly effective” at inactivating microbes. As more hospitals employ UV-C technology to disinfect air and surfaces, HAI rates will undoubtedly decrease, resulting in fewer unnecessary deaths.

Meanwhile, the UV industry continues to develop new UVGI products for specialty applications in healthcare environments. For example, UVGI has also been effective in keeping healthcare facility restaurant and food-service ice machines free of biological slime. A new mini UV lamp model has been developed for use in ice flakers/water dispensers at nursing stations, to prevent slime buildup and help reduce microbial load.

Aaron Engel is vice president of business development for Fresh-Aire UV, North America’s largest manufacturer of UV-C and photocatalytic oxidation (PCO)/activated carbon indoor air quality products.