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How Effective Are Ultraviolet Air Purifiers?

The thought that bacteria, viruses, and other microorganisms could be wafting through the air in your home, or resting in the folds of your air filter, can be frightening to some and disgusting to many others. The promise of simple device to kill all of these contaminants passively seems too great an opportunity to pass up. Many companies sell or recommend the installation of ultraviolet air purifiers and filters, but just how effective are these filters actually?

How They Work

When a UV purifier is described, images of a science fiction-like disinfection chamber may come to mind. The intricacy of a UV filter can be different, depending on how advanced it is, but in the end you’ll find that any in-duct UV filter is simply a light bulb in a box. The important thing is how well designed that light bulb and box are.

UV-C, -B, and -A (respectively) as they're filtered by Earth's ozone layer

UV-C, -B, and -A (respectively) as they’re filtered by Earth’s ozone layer

Ultraviolet light is a very broad range of electromagnetic frequencies of light. The light used in standard in germicidal lamps (the bulbs used for UV filters and purifiers) emits Ultraviolet C (UVC) light. UVC light is a shorter wavelength of light which cannot penetrate through the Earth’s ozone layer. Because of this, we’re protected from UVC emitted by the sun (which is a very good thing).

UVC light damages cells, leading to the inactivation and destruction of smaller organisms or severe damage in multi-cellular organisms (humans for example). By placing a specialized UVC-generating lamp inside the ductwork of your home you can disinfect the air as it passes through the system. Many of these systems have the added benefit of disinfecting surfaces which commonly trap moisture, if installed in a way that exposes those surfaces to the light.

To return to the beginning of this section, a UV purifier, when taken apart, really does look like a lamp in a complicated box. But you should never take a purifier apart, the UVC lamp inside is hazardous for direct exposure. You should never expose your skin or eyes to direct UVC from germicidal lamps of any kind.

True Effectiveness

So how effective are germicidal lamps and UV purifiers? That’s a complicated answer because UV light is very effective at disinfecting organisms and contaminants, but it takes time and certain qualities of your system can impede how well your purifier works. The effectiveness of your purifier is based on:

  • Air Flow Rate
  • Cloudiness
  • Light Intensity
  • Recirculation

To be effective at disinfecting your air, you need an intense UV light which shines directly on the contaminants for long enough to inactivate (kill) the mold spores, bacteria, and viruses present in your air. If a fresh source of microorganisms is constantly being fed into your recirculation system, it will also impact how clean your air is.

To account for this, a system which prolongs the time that air is circulated through the intense UV light is necessary. This is either done using a series of baffles to keep the circulating air in front of the light for longer, or by using a series of UV lamps to keep air exposed for long enough to disinfect it.

Having an effective dust and particulate filter is also key. Allowing dust and large particles, which are not destroyed by UVC light, can lead to cloudy air and obscured lamps as the dust settles on the bulb and reflective surfaces of your purifier. Keeping a clean air filter is essential to proper UV purifier operation.

What to Look For

Many people argue the benefits of simple UV purifiers, but they are not all created equally. Many air purifiers also generate a great deal of ozone (which is not healthy for indoor air at all). Others are low-budget systems which use a single lamp that is incapable of disinfecting more than a minor portion of the contaminants in your air.

Quality UV purifiers are expensive, but cheaper options are often more of a placebo than actual protection against infections. When you’re selecting a purifier for installation, be sure to double check that it is actually capable of meeting its claims and that it isn’t a system which produces excess ozone.


We’ve already mentioned that an air filter is necessary for proper UV light operation (keeping your ducts and UV lamp clean and free of airborne particles which block light), but there are other ways to keep your air contagion free as well.

While you can never completely remove mold from a home (mold spores are everywhere), you can keep it from growing by regulating the humidity in your home and cleaning up sudden outbreaks of mold. Keeping your house clean is the most effective method of limiting the spread of disease, viruses, and mold.

Another option is to have a high-efficiency particulate air (HEPA) filter installed in your home. These filters are used in hospitals and industrial clean-rooms to block the smallest particles, allergens, and viruses possible. To be clear, HEPA filters will not fit in the same slot or tray that a standard filter will. Installation of a new HEPA filter will require a professional installation to account for the large size of the filter, and the filters themselves can be fairly expensive. But if you struggle with allergens or need to improve resistance against disease, the combination of a HEPA filter and quality UV air purifier cannot be beaten.

For more advice on air quality and filtration systems, call your home comfort experts at (217) 866-1596 for your Free Whole Home Inspection and Analysis. We are available 24 hours a day, 7 days a week to answer any questions you might have.

We also offer an ongoing Home Maintenance Plan to help ensure you not only have regular heater/furnace maintenance and tune-up checks, but also saves your money!

Cassel Home Comfort Heating & Cooling, situated in the Champaign IL, is committed to being your best HVAC contractor choice in Central Illinois in both Value and Customer Service!