What Is A UV Air Purifier?
UV air purifiers are a safe air purification system that uses short wave ultraviolet light to inactivate microorganisms and pathogens in the air. It helps sanitize indoor air so you can enjoy breathing in cleaner air and sleep better. You will live healthier and benefit from a stronger immune system as exposure to harmful pathogens is reduced.
UV air purifiers can be a standalone unit or as part of the multi-stage filtration air purifier to complement the HEPA filter, activated carbon filter, or ionizer. It is commonly referred to as UV-C sanitizer, ultraviolet germicidal irradiation (UVGI), or UV germ killers. UV air purifiers are available in both residential and commercial settings. You can find UV technology used in hospitals, medical facilities, laboratories, meat processing, plants, HVAC system, and manufacturing factories as part of the infectious control group. 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.
- Prevent secondary allergies from triggering.
- Uses less energy than a conventional air purifier.
- Portable, travel-friendly form. Fits a plug-in model, wand/ wave, or wearable size.
- Less maintenance and cleaning are needed.
- Quiet operation.
- Expensive for standalone unit.
- 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.
- Might kill good bacteria or viral proteins in biomedical products.
- Potential health risks if it is not installed properly.
- Overdosage can degrade plastic, polymers, and dyed textile.
- Some UV lamp contains toxic mercury that can leak out when the lamp is broken or not disposed of properly.
How Do UV Air Purifiers Work?
Indoor air is forced into the air purifier’s internal chamber with a UV lamp for disinfection. Inside, The UV-C light irradiates short-wavelength at 254nm to break down mold, bacteria, virus DNA cells, and other pathogens that pass through. With the nucleic acids destroyed, the microbes will be killed or left incapacitated and rendered harmless. 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.
Is UV Air Purifier Effective?
UV air purifiers short wavelength can effectively inactivate or kill 99% of microorganisms like mold, mildew, germs, bacteria, and viruses from multiplying by altering their DNA/ RNA. A study by Duke University Medical Center and the University of North Carolina Health Care concluded that UV light help reduces more than 91% of pathogens in a hospital.
UV air purifier does have its limitation, according to Dr. Patricia Fabian, a Boston University professor specializing 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 impact indoor air quality positively. The EPA also concurs that a UV-C air purifier is less effective than a standalone unit because it cannot trap microscopic particles like a HEPA filtration system. It should be used cautiously to avoid damaging the eyes and skin during prolonged exposure.
Below are factors that will also play a role in UV sterilization, including:
- UV-C Light exposure time – The longer the drawn pathogens dwell inside the UV chamber, the more allergens will be inactivated. A 1-inch UV lamp will take 1-3 min to disinfect an E. coli bacteria, while a smaller UV sterilization box will take a lengthier 5- 10 min.
- Proximity to the UV-C lightbulb – The closer the pollutants contact ultraviolet light, the better they will be sterilized.
- The material (phosphor, quartz, LED) and type of lightbulb (UV-A, UV-B, UV-C) – Older models use low-pressure mercury lamp that emits >90% UVC radiation at 254 nm. The newer Excimer lamp/ Far-UVC has a peak emission of around 222 nm. Pulsed xenon lamps are commonly used in hospital settings that emit a short pulse of a broad spectrum. The latest light-emitting diodes (LED) are the default option because it is safe and contains no mercury. The LED UV radiation is at a narrow wavelength that peaks at 280 nm.
- The number of lightbulbs – The greater the number, the stronger the sterilization.
- Airflow cooling effect – Air Changes per Hour (ACH) measures the number of times the total air volume in a room has been cleaned or exchanged in an hour. The higher the ACH, the bigger the room size an air purifier can cover.
- The size of the models (desktop, tower, console, plug-in) – The bigger the unit, the more powerful the UV.
- UV-C light intensity and brightness (254 nanometers) – The UV lightbulb has a limited efficiency that gradually drops about 15% of its power annually. Most phosphor or quartz materials made UV light bulb has a lifespan of 5,000-10,000 hours that requires replacing promptly. The lamp’s durability, temperature, humidity, and design will also impact UV performance. Replace the lightbulb to restore its effectiveness.
- The strain of the pathogens in resisting UV radiation – Some bacterial and mold spores require a longer exposure time and higher UV light radiation to penetrate the cell.
UV Air Purifiers’ Effectiveness Guide
|Type Of Pollutants||UV Effectiveness||Exposure Time|
|Large particles (dust, debris, hair, fiber)||Ineffective||10-60 minutes|
|Fungi (mold spore, mildew)||Very effective||1-30 minutes|
|Germs, bacteria, and viruses||Very effective||1-30 minutes|
|Pet dander, asbestos||Ineffective||10-60 minutes|
|Light smoke and odor||Ineffective||10-60 minutes|
|Toxic fumes (VOCs, ozone, radon, CO, CO2)||Ineffective||10-60 minutes|
Are UV Air Purifiers Safe?
Ultraviolet light from the air purifier is safe, as long as you are not directly exposed to it. Most UV air purifiers use short-wavelength UVC light to destroy pathogenic microorganisms like mold, germs, bacteria, and viruses. It is harmless to use daily, with no chemical byproducts to worry about. You will sleep better, breathe better, and enjoy better air quality throughout the day.
That being said, all UV light will emit insignificant ozone under the 0.070 ppm 8-hour limit approved by the California Air Resources Board (CARB) and EPA. Ozone (O3) is a dangerous, highly reactive gas composed of three oxygen atoms. Through photolysis, air exposed to UV light can create ozone, where nearby oxygen will break apart and attach to other oxygen molecules to form ozone (O3). Exposing to even a small amount of ozone can lead to chest pain, coughing, shortness of breath, wheezing, inflammation, and throat irritation. In the long run, it can aggravate asthma and cause irreversible damage to our respiratory systems, like pneumonia, bronchitis, and lung scarring with reduced capacity. Children, elderly, asthmatic, and sick people with compromised immune systems will be more susceptible to ozone.
To rectify that, most UV air purifiers come with a coated lamp or ozone block that reduces 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 will not irritate the lungs and has no adverse effect on our health.
Another thing to point out is that a UV air purifier is not an ionic air purifier, even though both disperse insignificant levels of ozone byproducts. Ionizer generates negative ions to bring down airborne pollutants, while UV air purifier uses ultraviolet light to destroy pathogens. Both devices are safe for home use, unlike an ozone generator. You can learn more about bipolar Ionization and UV-C light technology here.
The Hidden Danger With UV Purifiers
Many health agencies, including the FDA and EPA, have reservations about appliances like UVGI, ionizer that emits hazardous ozone gas byproducts. Improper handling of UV air purifiers can worsen indoor air quality instead of improving it. Besides the ozone concern, direct exposure to ultraviolet light can lead to skin burning, eye damage/ photokeratitis, premature aging, and skin cancer.
To prevent the air cleaning appliances from doing more harm than good, here are some easy tips on how to use a UV sanitizing device safely:
- According to World Health Organization (WHO) guideline, never sterilize your hands or any part of the skin with unknown UV light.
- Avoid unreliable, poorly made UV air purifiers that have the tendency to leak mercury and harmful UV during irradiation.
- Do not let children or pets go near a UV air purifier unsupervised.
- Never stare directly at ultraviolet light. Never point the UV light at other people’s eyes as well.
- Avoid purchasing aftermarket UV lightbulbs or lamps that may not follow the FDA Ultraviolet Index (UVI) safety ratings.
- CDC recommends installing UV disinfection in ductwork or at the ceiling to complement the existing air filter rather than replacing it.
- For commercial use, make sure all safety measurements are practiced and properly suited to operate special UV devices.
What Is Ultraviolet Light?
UV or Ultraviolet light is invisible electromagnetic radiation with a wavelength from 10 nm to 400 nm. UV light is shorter than visible light but longer than X-rays as part of the sunlight spectrum. UV radiation contributes about 10% of the total sun's output. Only UVA and UVB will reach Earth as the ozone layer absorb UVC rays. Historically, ultraviolet light has been used to disinfect water supplies and surface area since 1908 in France. Close to home, it was 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 welders, bottle sterilizers, medical equipment, lamp, and air cleaner. The FDA regulates companies that manufacture, repackage or import UV medical devices in the United States.
Light comprises 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, it 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. Conversely, the longer the wavelength, the slower the vibration and the lower the energy.
Different forms of light have a broad range of UV wavelengths and energy levels. For example, ultraviolet light has a short wavelength between 100 to 400 nanometers, while visible light has a wavelength between 400-700 nanometers. Infrared light has a longer wavelength, between 700 nanometers to 1 millimeter; you can feel the heat in this range.
Ultraviolet Light: UV-A, UV-B, and UV-C
UVC lamps with different materials absorb and reflect different wavelengths of light. The shorter bands and higher frequency UV light has, the stronger energetic UV radiation will be produced. In general, ultraviolet light is subdivided into three categories:
- UV-A - The longest and least hazardous ultraviolet light. Long-wavelength 315–400 nanometers photons vibrate the slowest. It is closest to the 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. It is responsible for people getting sunburned (inflammatory, skin redness) after a day at the beach. Overexposed to UV-B rays can also cause skin cancer and damage your DNA cell. 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 with the most energy. The ozone layer will absorb UVC rays from the sun before it reaches Earth. UV-C lights are effective yet silent, mostly odorless, and invisible to the human eye. However, prolonged exposure to UV-C light can cause permanent damage to DNA, eye, and skin cancer. Fortunately, Earth's ozone layer will absorb 100% of UV-C radiation. UV-C light is commonly used in sterilizing devices, including air purifiers, to disinfect germs, bacteria, and viruses.
The Effectiveness Debate
Another setback with UV technology is its efficiency. While there is no doubt UV air purifiers can inactivate germs, bacteria, viruses and stop them from multiplying, it takes around 12.5 seconds to kill 99.9% of the virus under ideal conditions. With the constantly moving airflow, it is unlikely the microbes will remain exposed in the internal UV chamber for minutes. Besides the UV-C Light exposure time, the pathogens will have to be close to the UV light bulb to be fully sanitized. Some microorganisms strain, like mold spores, is highly resistant to UV radiation and may even take longer to kill off. Ultraviolet light is not great in removing large particles like dust, hair, and dirt from the air. It is also ineffective against smoke, odor, and chemical fumes like VOCs. The material of the lightbulb, like phosphor, quartz, and LED, also plays a big part. Avoid any mercury-based lamp that poses hazardous risks. The ultraviolet light intensity/ dosage, the cooling effect of airflow, ACH, and room size, can also affect the UV irradiation performance.
The lack of standardized UV measurement against airborne pollutants is another common issue. Some manufacturers sell inferior products yet make up fake claims on the UV effectiveness to trick people into buying one. You should only purchase a HEPA air purifier with UV light from a reputable manufacturer approved by CARB and AHAM.
The Safer Option: UV + HEPA
Rather than entrusting entirely to UVC light, the better and safer option is to combine conventional HEPA filtration with UV technology, according to EPA. A HEPA air purifier can quickly capture 99.97% of airborne pollutants as small as 0.3 microns. The activated carbon filter will absorb smoke particles, chemicals, and fumes. The UV light will supplement the filtration by destroying 99.9% of trapped allergens, so there is no chance of the microbes multiplying and reintroducing back into the air. This combination can help slow down the spread of COVID-19 viruses, as recommended by CDC. A life-saving device during these unprecedented times.
The FDA regulates electronic products (non-medical and medical) that emit UVC radiation through the Electronic Product Radiation Control Provisions. Firms that manufacture, repackage or import medical devices in the United States must meet the definition of a medical device under section 201(h) of the Federal Food, Drug, and Cosmetic Act. Ask the manufacturer about the air purifier's health and safety risks, particularly ozone emissions, to ensure you are getting the real deal. Find out if the UV lamp material contains mercury, which can be hazardous if the lamp is broken. You can read more about UV radiation and disinfection in FDA website. Alternatively, contact 1-888-INFO-FDA, or the Office of Health Technology for more technical information. You can also refer to the complete reports and sources below.
What About Ionizer? Are They The Same?
While both are safe for home use despite creating little ozone, ionizers and UV air purifier use different technology to clean the air. Ionizers or ionic air purifiers release safe negative ions that adhere and pull down airborne pollutants. Do not confuse it with an ozone generator. UV air purifiers sterilize microscopic airborne pathogens leaving no traces behind. It is the superior and effective air cleaning method. You can learn more about the differences between ionic VS UV air purifiers here.
Does UV Light Kill COVID-19?
Studies have shown that UVC light in an air purifier or HVAC system can disinfect airborne COVID-19 particles and viruses (including H1N1), common cold pneumonia, SARS, MRSA, strep, TB, E. coli, measles. UVB and UVA radiation are less effective than UVC at inactivating the SARS-CoV-2 Coronavirus. 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. Another study done by nature.com discovered that far-UVC light kills 99.9% of airborne Coronaviruses in 25 minutes. However, ultraviolet rays cannot prevent COVID-19 infection or kill the virus in infected patients. It can only reduce the risk and should not be your only tool to protect from SARS-CoV-2. EPA agency recommends wearing face masks and practicing social distancing with air filtration systems.
Which Is Better: HEPA Filter Or UV?
While both filtrations can remove airborne particles in the air, UV-C air purifiers are technologically superior to HEPA. HEPA filters only capture live pollutants in the air with a higher capacity volume. It does not eradicate the particulate and requires replacing when full. Otherwise, there is a risk of the pollutants reintroducing back into the air. UV air purifiers destroy contaminants permanently and prevent further growth. Best used against bacteria and airborne viruses smaller than 0.1 microns.
Which Is Better: UV Light Or HEPA Filter?
Both have 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 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 the trapped microorganisms from growth and reintroducing back into the air is a risk, proper maintenance and regular filter change can mitigate the risk.
How To Choose the Best Air Purifier With UV Light?
Some models focus on the power of germicidal irradiation, while others offer an affordable price point. Regardless of which direction you go with, always choose a model that passes the CARB requirement. You will find ARB Certified label in the packaging of the air cleaner. Do pay attention to the UV light intensity, airflow delivery rate, the type of lightbulb, and the size of the air purifier.
Note that UV light does not fall under AHAM testing. Some manufacturers will exaggerate the performance output or make false claims 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
You can read the full product reviews, specification comparisons, pricing, and UV light strength in handling airborne pollutants in our best UV air purifiers here.
By the end of this post, we hope you will have no doubt about UV air purifiers' effectiveness against pathogens. If you want the best of both worlds, we recommend getting a HEPA air purifier with a UV light that uses multiple filtrations to destroy airborne pathogens and purify the air. It is better at destroying airborne microorganisms and pathogens. It is much more effective than a stand-alone UV sanitizer because it will cover a wide array of airborne pollutants. There is less risk of harmful ozone byproducts as the other filter media will chip in with the air cleaning.
In any case, managing the source of indoor air pollution should be your primary focus for a long, healthy indoor air quality. Improve home ventilation by opening windows and doors. Place the UV air purifier close to your breathing zone, where you spend the most time e.g. bedroom. Lastly, reduce the dependency on gas stove appliances and seal/ replace asbestos materials in the home.