Given time, UV air purifiers are effective at killing microbes.
Are UV Air Purifiers Effective?
Yes, UV air purifiers do work as it is scientifically tested by independent research studies and recommended by CDC, EPA. The short wavelength UV radiation can effectively inactivate and kill microorganisms like mold, germs, bacteria, viruses. However, UV air purifiers are less effective in removing dust, pet dander, smoke, odor, and chemical fumes like VOCs.
The effectiveness of UV-C light in an air purifier depends on a number of factors including:
- Exposure time in the UV chamber (the longer the better).
- Proximity on how close the pollutants come into contact with the ultraviolet light.
- The material and type of lightbulb (UV-A, UV-B, UV-C).
- Cooling effect of airflow.
- The size of the models (desktop, tower, console).
- UV light brightness and intensity.
- The strain of the pathogens in resisting UV radiation.
UV air purifier does have its limitation, according to Dr. Patricia Fabian, a Boston University professor that specializes in housing, indoor air, respiratory infectious disease transmission, and GIS. The limited airflow means it is unlikely pathogens in the air will be exposed sufficiently in the UV chambers for sanitization. You will have to rely on other filtration systems to make a positive impact on indoor air quality.
What Is A UV Air Purifier?
UV air purifiers are a safe air purification system that uses ultraviolet light to inactivate microorganisms in the air. It helps sanitize indoor air so you can enjoy breathing in cleaner air and live healthier. UV air purifiers can be a stand-alone unit or as part of the multi-stage filtration air purifier to complement the HEPA filter, activated carbon filter, or ionizer. It is often referred to as UV-C sanitizer, UVGI air purifier, and UV germ killers. UV air purifiers are available in both residential and commercial settings. UV technology is often used in hospitals, medical facilities, laboratories, meat processing plants, and manufacturing factories to assist with disinfection.
For home use, different sizes can be found such as a portable variant for desktop use, wall plug-in air cleaner, slim tower form, or whole-house paired with the HVAC system.
Here are the pros and cons of a UVC air purifier.
- A safe disinfection technology that is widely used in hospitals and healthcare centers.
- Improves indoor quality by removing airborne biological pollutants, chemical fumes, and odor.
- Halt the reproduction of microorganisms like mold, bacteria, and viruses.
- Uses less energy than a conventional air purifier.
- Less maintenance and cleaning are needed.
- UV light bulb requires replacing as the radiation intensity will deteriorate over time.
- Less effective against smoke, dust, and large particles.
- Emits ozone but at an insignificant level.
How Do UV Air Purifiers Work?
Indoor air is forced into the air purifier’s internal chamber for disinfection. The UV-C light irradiates short-wavelength at 254nm to breaks down mold, bacteria, and virus DNA cells. With the nucleic acids destroyed, the microbes will be killed or left incapacitated and rendered harmless as it loses the ability to reproduce and causes allergies. UV air purifiers that combine UV light radiation with Titanium Oxide can further reduce volatile organic compounds (VOCs) in the air via catalytic molecules. The sanitized air will be expelled out and recirculated back into the room. The visible UV irradiation runs silently in the background and is safe for children and pets use. To avoid corneal sunburn (photokeratitis), one should not stare directly at ultraviolet light.
Note that the UV light bulb efficiency will degrade over time. Most phosphor or quartz materials made UV light bulb has a lifespan of 5,000-10,000 hours that requires replacing promptly. The durability of the lamp, temperature. humidity and design will have an impact on UV performance.
What Is Ultraviolet Light?
UV or Ultraviolet light is a type of invisible electromagnetic radiation with a wavelength from 10 nm to 400 nm. As part of the sunlight spectrum, UV light is shorter than visible light but longer than X-rays. UV radiation contributes about 10% of the total sun’s output. Only UVA and UVB will reach down on Earth as UVC rays will be absorbed by the ozone layer. Historically, ultraviolet light is used to disinfect water supplies and surface area since 1908 in France. Close to home, it is also used during the 1930s to prevent the spread of measles in Philadelphia schools. Now, you can find UV in black light (backdrop), tanning beds, arc welder, bottle sterilizer, medical equipment, lamp, and air cleaner.
Light is made up of a tiny discrete amount of particles or quantum of electromagnetic radiation called photons. Photons will transmit a high level of electromagnetic energy when they encounter matter. As the light travel, they will send vibration back and forth creating a trace of light wavelength. The shorter the wavelength, the quicker the vibration thus the higher the energy released. Different forms of light have different wavelengths and energy levels. Ultraviolet light has a short wavelength between 100 to 400 nanometers. Visible light has a wavelength between 400-700 nanometers. Infrared light has a longer wavelength between 700 nanometers to 1 millimeter.
Ultraviolet Light: UV-A, UV-B and UV-C
The shorter bands UV light has, the stronger energetic UV radiation will be produced. In general, ultraviolet light is subdivided into 3 categories:
- UV-A – The longest and least dangerous ultraviolet light. Long-wavelength 315–400 nanometers photons that vibrate the slowest. It is closest to surface area and covers around 95% of the sun’s radiation. Commonly used in tanning booths or disinfection tools. Overexposed to UV-A can cause skin wrinkles and premature aging.
- UV-B – Medium-wavelength, 280–315 nanometers photons that vibrate slightly faster. It is often used in plant development to alter plant hormones. Overexposed to UV-B rays can cause sun burning, skin cancer, and damage your DNA. The good news is about 95% of the UV-B light is absorbed by Earth’s atmosphere.
- UV-C – The most harmful UV light to living organisms and cells. Short-wavelength, 100–280 nanometers photons that vibrate the fastest. UVC rays from the sun will be absorbed by the ozone layer before it will reach down on Earth. Prolonged exposure to UV-C light can cause permanent damage to DNA, eye, and skin cancer. Fortunately, 100% of UV-C radiation will be absorbed by Earth’s ozone layer. UV-C light is commonly used in sterilizing devices including air purifiers to disinfect germs, bacteria, and viruses.
We recommend getting a HEPA air purifier with UV light that uses multiple filtrations to purify the air. It is much more effective than a stand-alone UV sanitizer because it will cover a wide array of pollutants in the air. There is less risk of harmful ozone byproducts as the other filter media will chip in with the air cleaning.
Does UV Light Kill COVID-19?
Studies show that UV light can be used to disinfect and kill airborne COVID-19 particles. A study published in the American Journal of Infection Control (AJIC) found that a high viral load of SARS-CoV-2 was killed after nine minutes of UVC exposure. However, ultraviolet rays cannot prevent COVID-19 infection or kill the virus in infected patients. UV light devices should also be used cautiously to avoid damaging the eyes and skin.
Do UV Air Purifiers Create Ozone?
During the process of UV radiation, some oxygen in the air (O2) will be transformed into dangerous ozone (O3) byproducts through photolysis. To rectify that, most UV air purifiers come with a coated lamp or ozone block that reduces the ozone emission to an insignificant level. The ozone emission level is below the 0.050 parts per million (ppm) concentration limit adopted by California Air Resources Board (CARB) for indoor use. Exposure to a low concentration level of ozone has no adverse effect on our health and will not irritate our lungs.
Which Is Better UV Light Or HEPA Filter?
Both have their pros and cons but UV-C air purifiers are more technologically advanced with superior sanitization. Ultraviolet light eradicates bacteria and viruses smaller than 0.1 microns including SARS-CoV-2 mutations that can pass through a HEPA filter. There is no chance of the deactivated pathogens from growing and spreading in the room. It also uses less energy than a conventional HEPA air purifier that requires a constant level of airflow to run. On the other hand, an air purifier with a HEPA filter can trap a large concentration of pollutants in one cycle. While there is a risk of the trapped microorganisms from growth and reintroduce back into the air, proper maintenance and regular filter change can mitigate the risk.
How To Choose the Best Air Purifier With UV Light?
There are many types of UV air purifiers designed for different target audiences. Some models focus on the power of germicidal irradiation while others offer an affordable price point that is hard to beat. However, UV-light does not fall under AHAM testing therefore some manufacturers will exaggerate the performance output or make false claims in order to boost sales. To help you bypass all the ineffective and dubious UV air purifiers with uncoated UV lamps, here are our best pick of the lot with multi-stage filtration.
- PureZone 3-in-1 True HEPA Air Purifier
- GermGuardian AC5250PT Air Purifier
- Pure Enrichment PureZone Elite Air Purifier
- GermGuardian GG1100W/ GG1100B Air Purifier
- HoMedics AP-T30 TotalClean 5 in 1 Air Purifier
- InvisiClean Aura II 4 in 1 Air Purifier
- SilverOnyx True HEPA Air Purifier