Facts About HVAC UV-C Light Air Quality Benefits
Note: Article updated on 5/11/2020 with the most current information based on CDC, ASHRAE and NADCA publications. Original publishing date 10/13/2015.
The HVAC professional who services your home of office building might ask if you would consider installing Ultraviolet (UV) lights inside your system. The reason for this question? The use of certain UV lights can reduce or prevent microorganisms from circulating within the duct-work of your home or office. This article explores the facts about how specific UV lights can accomplish this task, and answers some of the most common questions about UV lights can help disinfect an HVAC system.
What Is UV Radiation?
Within the light spectrum, ultraviolet light waves occupy the 0 nm to 400 nm range. The term nm stands for nanometers, or billionths of a meter. This range is optically invisible to the human eye. The 0 to 400 nm spectrum is divided into 4 levels1, and they are defined as:
- UV-A (long-wave; 400 to 315 nm): the most abundant in sunlight, responsible for skin tanning and wrinkles.
- UV-B (medium-wave; 315 to 280 nm): primarily responsible for skin reddening and skin cancer.
- UV-C (short-wave; 280 to 200 nm): the most effective wavelengths for germicidal control.
- UV under 200 nm (vacuum UV; 0 to 200 nm): radiation below 200 nm can produce ozone (O3) in air.
It is the UV-C section of the spectrum that has germicidal properties, with 253.7 nm being the ideal frequency level at which DNA absorbs the most UV light.
HVAC UV Lights – 5 Common Questions and Their Answers
Are Viruses and Bacteria Within My HVAC System a Health Concern?
Yes, and this has been scientifically proven. Contamination in HVAC units is a widespread issue that shouldn't be ignored. This contamination often contributes to building-related diseases, like viral or bacterial infections, allergic rhinitis, asthma and hypersensitivity pneumonitis, according to the National Institute of Health. But only certain UV lights can be used in air purification. The Ultraviolet Germicidal light (UVGi) can help eliminate many types of bacteria and viruses. The UVGi light operates within the UV-C spectrum, which is the effective wavelength spectrum for germicidal efficiency.
Can UV Lights for HVAC Really Increase the Air Quality in My Home?
Yes, if they are installed properly, and use the correct spectrum of UV light. It is up to the homeowner to ensure that conditions are right, and installation is completed correctly by a qualified HVAC technician. A professional with experience in installing UVGi systems must keep a multitude of conditions in mind when installing a system2. The correct placement and direction of the proper number of UVGi lights has as much bearing on effectiveness as the temperature and humidity levels within the home.
Does Air Filtration Help?
Absolutely. As a matter of fact, the CDC recommends that a High Efficiency Particulate Air (HEPA)-level air filter be used to trap larger particulates3. This is important because the presence of particulates can shield a microorganism from UV light bombardment. The CDC suggests using Ultraviolet Germicidal Irradiation (UVGI) as an adjunct air-cleaning measure, as it cannot replace HEPA filtration.
What Types of HVAC UV Light Systems Are Available?
UV light installations for HVAC come in two types; coil sterilization and air sterilization. Air sterilization is also called an In-Duct UVC system, and with this method, the UV-C light disinfects the air as it cycles through the return ducts. By enhancing the reflective surface within that section of the duct work, the UV-C light is maximized in all directions, making it more efficient. With coil sterilization, UV-C lamps are installed to target sensitive and problem-prone components such as cooling coils, condensation pans, and filters. This allows targeting of microbial growth in tougher-to-reach areas such as grooves, fins, seams and edges.
Is Operating an HVAC UV Light System Costly?
Post-installation, the electrical consumption and bulb replacement will become two expense areas for your UV-C system. For electricity consumption, you can easily approximate energy use by using an Amps-to-Watts calculator, and then a Watts-to-Electricity Cost Calculator4. Amps/Watts are usually listed on the actual UV-C bulb and in the operator’s manual that comes with the installation.
HVAC UV Light Safety Warning that Must Not Be Ignored
We are all familiar with common-sense warnings about too much exposure to the sun, as excessive UVA or UVB exposure can cause skin damage, and in some cases, skin cancer. Direct exposure to the UV-C used in HVAC systems is hazardous, particularly to the skin and eyes. Eye damage can be considerable and sometimes permanent, so careful handling and installation by a qualified technician is an absolute must. A qualified professional will take the proper precautions during installation, to ensure that no UV-C light ever reaches an occupant’s eyes.
Proper air filtration is the first line of defense against the circulation of microbes within your HVAC system. With the right conditions and proper installation, UV lights can be very effective at killing viruses, mold, and bacteria. The two working together can make your home or office building a much healthier place.
1 On the internet at ASHRAE organization website located at https://www.ashrae.org/file library/technical resources/covid-19/si_s16_ch17.pdf, UV chart is within the opening paragraph. Accessed on May 6, 2020.
2 On the Internet at NADCA website located at https://nadca.com/sites/default/files/images/2016/nadca_white_paper_on_uv_lighting_applications.pdf, Section “Typical Use” accessed on May 6, 2020.
3 On the internet at the CDC website located at https://www.cdc.gov/infectioncontrol/pdf/guidelines/environmental-guidelines-P.pdf Page 27, Section 3a, accessed on May 6, 2020.
4 Calculators available at https://www.rapidtables.com/calc/electric/index.html.
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