Ultraviolet-C Lighting Cuts Air Handler Maintenance in Airports, Boosts Efficiency and Indoor Air

Nearly 3.5 billion people flew worldwide during 2015, according to the World Bank. That’s almost half the global population. A key component of serving those countless passengers is maintaining healthy, comfortable indoor environmental quality (IEQ) in airports.

To achieve this, airport facility management teams around the globe are tasked with maximizing performance efficiencies, while reducing maintenance calls for their air handlers, which can number in the hundreds.

Commercial air handling equipment in airports is designed to condition (cool or heat) a space, as well as provide adequate ventilation rates. Inevitably, though, air handlers become less energy efficient as mold, biofilm and other organic compounds accumulate on cooling coils, restricting airflow and shortening equipment life. Evidence shows that up to a 25 percent drop in capacity can occur within five years or less of startup.

As coil performance degrades, the ability to maintain temperature set points can be compromised, due to a decrease of heat transfer and restricted air flow brought about by increased coil pressure drop. Furthermore, inefficient air handler performance can degrade the quality of air in compact spaces, such as airport terminals, and keep potential disease-causing microbes circulating throughout.

In an attempt to clean coils, facility managers often resort to manual pressure washing or chemical treatments—these methods are costly, labor-intensive and, worst of all, temporary. The coils will foul again and require further attention.

A much more efficient and permanent solution to coil fouling and the inefficiencies it brings is Ultraviolet-C (UV-C) technology, which uses light in the UV-C spectrum to degrade organic matter. Ionization drives UV-C’s power to alter chemical bonds, causing lasting damage to DNA, ultimately killing or inactivating the microorganism. Over time, the 253.7nm germicidal wavelength also reflects deep into the coils to eliminate the build-up that mechanical and chemical washing often misses.

The Three-Fold Impact of UV-C

UV-C lamps have been used to disinfect upper air streams in hospitals and doctors’ offices since as early as the 1940s. During the 1990s, the technology was applied to the cleaning of HVAC/R components and has been developing ever since. It offers the three-fold benefits of improved energy efficiency, higher IEQ and reduced maintenance.

Primarily now installed to destroy microorganisms that accumulate on HVAC/R components, particularly cooling coils, UV-C lamps boost energy efficiency. Retrofitted UV-C lamps can help return A/C units to initial capacity and reduce or eliminate costly coil and plenum cleanings in as little as 90 days, while new system installations maintain “as-built” conditions. The UV-C energy penetrates deep into the coil to eliminate build-up that cannot be reached by either mechanical (pressure washing) or chemical treatment, and the overall improved heat transfer efficiency and reduced coil pressure drop can slash energy use by 10-25 percent on average.

A direct result of an efficiently-running HVAC/R system is improved IEQ, a necessity wherever large groups of people gather, such as in airports. An inefficient HVAC/R system can contribute to poor indoor air through decreased air flow, causing the same bacteria and viruses to circulate throughout a space, increasing the chance of illness. Naturally, the more people there are in a space, the more microorganisms can be generated and proliferate. UV-C has proven to be an effective solution. A 2013 CDC-funded study conducted in two hospitals found that UV-C reduced the total number of colony-forming units of any pathogen in a room by 91 percent. The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), too, has recognized that the UV-C wavelength inactivates virtually all microorganisms living on HVAC/R surfaces with a kill ratio of 90 percent or higher, depending on UV-C intensity and length of exposure.

UV-C can do all of this cost-effectively, with an average installed cost of 15 cents per cubic foot per minute, or CFM (many users report costs that are even less). Using a 10,000 CFM system as the example, the UV-C fixtures would cost $1,500, with an annual operating cost of $188 at $0.10/kW – operating 24/7/365. That is less than one percent of the average 18 percent power savings gained through a more efficient (better heat transfer & lower pressure drop) air conditioning system.

Furthermore, field reports indicate that the initial cost of a UV-C system is roughly the same as one properly performed coil-cleaning procedure, and less when system shutdowns, off-hours work with the associated overtime, and/or contractor labor costs, are considered. Indeed, without UV-C, cleanings are necessary at least once per year to remove capacity-starving pathogen buildup, but cannot reach pathogens deep in the coil and can also worsen the situation by compacting biomaterial in the coil. With staffs and budgets shrinking, however, time and money for in-house or contracted coil cleaning is becoming scarce. As a result, it might be more rational to make a one-time investment in a UV-C system that will keep cooling coils at as-built conditions.

Once installed, the only maintenance that UV systems require is lamp replacement. Most lamp manufacturers (Phillips, GE, and Sylvania, etc.) recommend replacing UV lamps annually, or every 8,760 hours. Thus, most facility managers employ an annual re-lamping schedule.

Annual replacement is recommended because it consolidates change-outs into one service interval, allowing the facility to purchase lamps in larger quantities to save money and time. This also reduces the need, with the exception of critical environments, to invest in an expensive radiometer or other equipment to monitor individual UV-C output. Knowledge that lamp replacement will simply be “taken care of” each year also allows peace of mind for facility managers.

Overall, UV-C’s ability to boost HVAC/R efficiency, improve IEQ and reduce maintenance time and costs makes it useful anywhere there are air handlers. With the potential for federal funding cuts impacting airports, UV-C can act as a simple, money-saving solution, as it recently did at LAX.

Case in Point: LAX Airport Restores HVAC System Performance Through UV-C

With nine terminals totaling several million square feet of floor space, Los Angeles International Airport (LAX) is massive. It’s also crowded: the 75 million passengers who passed through it in 2015 made it the world's seventh busiest airport.

Keeping those travelers comfortable and safe falls to the airport’s facility management teams, who routinely look to boost efficiencies and decrease maintenance calls across their immense service area. So when a tenant in Terminal 2 complained of a musty smell in their offices, the teams kicked into action.

“We quickly determined that the odor resulted from the buildup of mold and bacteria on the air handler evaporator coil; a very common condition, especially given our humid, seaside environment,” recalls Richard Yakel, the airport’s air conditioning supervisor.

Although Yakel’s maintenance crews could remove the mold with solvents and elbow grease, he knew that mechanical cleanings and antimicrobial agents were only a temporary solution. Moreover, the organic buildup on the coil had caused a pressure drop that reduced the volume of air passing through the coil, as well as its heat-transfer efficiency.

Seeking a more permanent solution, Yakel turned to UV-C. Although a proven technology, Yakel wanted to verify UV-C’s performance before committing to using it airport-wide, so he decided to conduct a test installation on the odorous air handler. His team first measured the unit’s static pressure using a differential pressure gauge as well as airflow levels. Following this baseline measurement, the team installed UV-C fixtures in the 14,000 CFM air handler. Pressure readings were taken monthly for the following six months.

“My team and I were surprised by how quickly the UV-C cleaned the HVAC evaporator coil, fan motor housing and blades. However, we were truly stunned to witness a 15 percent (2,000 CFM) increase in airflow levels after just a week of operation,” says Yakel.

The experiment’s timing proved fortuitous. The airport was in the initial stages of planning a multi-year, $4.11 billion improvement and redevelopment project that would include renovation of existing facilities, as well as a major expansion of the Tom Bradley International Terminal.

With budget funds available for HVAC/R improvements, Yakel made a successful case for equipping all of the airport’s 200+ air handlers with UV-C as a way to enhance indoor environmental quality for passengers and employees.

“Our application requires the most durable equipment. Anything we specify has to run 24/7 and it has to last for at least 20 years,” notes Yakel. “It has to be compatible with new and existing air handlers and other system components, as well as the building management and remote monitoring systems.”

Each of the airport’s terminals has multiple air handlers, ranging from five in Terminal 1 to 30 in Terminal 4. Air handlers range in cooling capacity from 10 to 40 tons; some of which have been in place for decades. None of this was a problem: UV-C works with any type of air handling equipment regardless of brand, capacity or age.

At the end of the first three-year contract period, more than 75 air handlers had been retrofitted with UV-C, which has reduced maintenance costs and freed crews up for other tasks. With union positions earning an average $28 per hour, the typical eight-hour physical air handler cleanings were each costing roughly $230 and needed to be performed on a quarterly basis. At nearly $900/year/AHU multiplied across 200 AHUs – the new technology could eventually save upwards of $180,000 annually in maintenance costs alone.

But Yakel sees cost and time savings as fringe benefits. His main goal was to improve IEQ for the millions of people who use the airport each year, and that has certainly been the case. "We haven't had any more complaints," he beams.

The president and co-founder of UV Resources, a provider of UV solutions and replacement lamps for HVAC systems, Daniel Jones is an ASHRAE Member and a corresponding member of the ASHRAE Technical Committee 2.9 and ASHRAE SPC-185.2, devoted to Ultraviolet Air and Surface Treatment. He may be reached at dan.jones@uvresources.com.