Healthcare UV tackles IAQ


Millions of residential and commercial ultraviolet (UV) light systems have been installed in North American HVAC systems in the last 10 years, and now the trend is expected to penetrate European and UK markets, says Michael Stensbjerg


UV GERMICIDAL irradiation (UVGI) is now gaining traction in the UK especially in healthcare facilities, schools, office buildings, hotels and other commercial prop- erties. UV light systems disinfect airborne microbes that circulate through HVAC systems. They also reduce coil cleaning maintenance as it’s proven to prevent mould and other biological contaminant growth on HVAC coils.


The disinfection factor has made UV a popular hospital appli- cation, because indoor air quality (IAQ) is critical to patron health. Thus, UV has been a critical com- ponent in the worldwide battle against hospital acquired infec- tions (HAI), which is a growing phenomenon plaguing many health institutions today. Consequently, many hospitals worldwide are installing HVAC systems’ coils with UV light sys- tems to combat airborne microbial contaminants.


Lack of awareness is the main reason UV technology in Europe hasn’t paralleled North American growth. Any scepticism as to whether UV technology works is steadily being reversed through many recently published laborato- ry studies proving UV light’s effec- tiveness in killing biological con- taminants such as mould, mildew, fungi, allergens and any airborne infectious diseases commonly transmitted in indoor environ- ments.


One recent study was conduct- ed by the third-party indoor air cleaning device test lab in Dublin, Ireland, Airmid Healthgroup (AHG). The test reported UV light was ‘highly effective’ at inactivat- ing microbes. It simulated airstream microbe inactivation in an ASTM/AHAM style environ- mental test chamber resembling a typical building’s HVAC air han- dler and indoor environment arrangement. A single pass test was also performed on an American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Standard 52.2 test duct system.


The test’s UV light single-pass inactivation results were: Bacteria (S.epidermidis)--98.85-percent;


Virus (MS2 coliphage)--99.03-per- cent; and Mould (A.niger)--78.80- per cent.


The test was performed as a sin- gle pass under typical indoor HVAC conditions of 73°F (23°C), 55 per cent relative humidity and airflow velocity of 492-fpm (0.93m3/sec). IAQ experts claim even higher inactivity rates among the three tested microbes could occur in a multiple pass environ- ment, such as a typical building HVAC recirculation strategy. UVGI technology is more than a century old especially for water purification, but just in the last 25 years, manufacturers have recently developed air filtering systems that inactivate microbes that pass through an HVAC system and reside on air handler interior sur- faces. UV light systems provide chemical-free disinfection that scrambles the microbe’s DNA so it can’t reproduce.


Not all UV light is the same. UV- A (used for black lights), UV-B (used in tanning salons and caus- es sunburns) and UV-C wave- lengths are all present in sunlight. However, higher frequency UV-C wavelengths of 256 nanometers (nm) are filtered by the Earth’s upper atmosphere. Therefore microorganisms, such as mould, have no experience or defense against it. UV-C light is strong enough to sterilise microbes, but not enough to degrade an HVAC system’s coil or interior surfaces.


UV coming to the UK


Three types of UV applications – commercial air handlers, mini-split air conditioners and ice machines – are expected to emerge in the UK HVAC market the next five years. • Commercial HVAC Coils: Most commercial coils can be outfitted with UV lamp(s) for disinfection as well as maintenance concerns. These systems come in lamp lengths of 32, 46 or 60-inches. They come with their own indi- vidual power supply and can be mounted in multiple configura- tions depending on the size of the coil and the required coverage. A typical configuration is a tubular rack-type of system where lamps


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clip onto common electrical con- duit tubing custom cut onsite to fit the coil. These systems can be installed in less than an hour. Power supplies should be weather resistant so they can be mounted inside the airstream or remotely outside the air handler. UV sys- tems aren’t switched off during HVAC system idle periods and work continuously to kill microbes around the clock. The system’s UV-C lamps need replacement in every one or two year increments.


UV light systems also add an


energy savings factor too, because even a micro thin layer of biologi- cal growth can decrease a coil’s heat transfer. Microbial growth left untouched on a coil can lead to premature corrosion and failure. • MiniSplit UV: Mini-split evapora- tor coils are particularly difficult for UV applications because of their restricted mounting space inside the inherently tight, cramped enclosure. Therefore, manufacturers have developed small pencil-thin UV technology lamps that can fit inside most manufacturer’s evaporator coil enclosures. The power supplies can easily be wired into the mini- split evaporator electronics. • Ice Machine UV: Ice machine microbes are many times over- looked or unseen by foodservice or hotel operators, but the effect of mould can affect the taste and odour of ice as well patron health. Ice machines are particularly sub- ject to mould in foodservice envi- ronments that bake or brew with yeast. Like minisplits, ice machines have tight spaces that need UV light systems specially designed and manufactured for ice environments.


VOC and microbial contaminants The future of total HVAC system air purification is the combination of microbial and volatile organic compounds (VOC) removal. Common VOC airborne contami- nants in commercial buildings are formaldehydes from furnishings, chlorine from cleaning chemicals and other invisible airborne sub- stances that can irritate or damage lung tissue.


UV light systems prevent mold and other biological contaminant growth on HVAC coils as depicted above


Since UV light is only effective against biological contaminants, manufacturers are combining new technologies called gas-phase air purification and photocatalytic oxidation (PCO) with UV in one unit to combat VOC and microbial contaminants, respectively. Gas-phase air purification uses activated carbon-based media to adsorb and hold VOCs through a chemi-sorption process. The PCO process uses the chemical reaction of UV-C light shone on titanium dioxide-infused carbon media, which captures and holds the con- taminants and allows the PCO process to convert them into harm- less carbon dioxide (CO2) and water vapor (H2O). This also elim- inates expensive media replace- ments associated with stand-alone, independent gas-phase air purifi- cation systems, because the same UV light that disinfects microbes, also regenerates the media through the PCO process. Combination UV, carbon media and PCO technology is so promis- ing that it won the IAQ Category of the Innovation Awards at the 2011 international trade show, AHR Expo in 2011.


IAQ is the next frontier for the UK and European HVAC industries and UV promises to be a major player when commercial facilities demand better occupational envi- ronments. • Michael Stensbjerg is president of Denmark-based Fresh Aire Europe/Airvention APS


Healthcare supplement to HVR | May 2016 | 25


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