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Ultraviolet Germicidal Irradiation for IAQ

Application of ultraviolet, or UV-C, light is emerging as a highly effective method of eliminating microbial growth in HVAC systems and in circulated air. Also known as ultraviolet germicidal irradiation (UVGI), UV-C targets microorganisms such as viruses (including coronavirus), bacteria, mold, yeast and protozoa, causing cell death and rendering microbes unable to reproduce. It has long been used as a germicide in applications including equipment sterilization and water purification and is increasingly being in HVAC systems.


Damp, humid conditions, such as those in an HVAC system, encourage the accumulation of organic materials and biofilm growth in condenser coils, air filters, duct surfaces, and drain pans. Left unattended, these materials can choke airflow and release contaminants and odors into the airstream. UVGI, which has long been used for equipment sterilization and water purification, inactivates the DNA and RNA of microbes and renders them unable to reproduce.


Two basic types of UV-C systems are used in HVAC: coil and in-duct, which are often used in tandem. ASHRAE recognizes the benefits of UV-C and has published recommendations for microwatts required to obtain these benefits. Coil treatment systems are more effective, as exposure is continual, whereas in-duct system exposure time is limited to the time it takes for the airstream to pass the light source. In-duct efficacy can be improved with the addition of more bulbs to subject microbes to higher UV dosage. Independent studies have shown microbe kill rates to average around 98%.


Payback on UV-C systems can occur in as little as six months, and further savings are realized through reductions in maintenance. Installation is inexpensive, costing about the same as a single professional coil cleaning. For more information on UV-C and how it can kill microbes and lower utility costs, please contact MSC at 973-884-5000.