4 Things to Consider Before Purchasing UV-C Sterilization Systems

With the spread of the COVID-19 coronavirus, sterilization and disinfection are likely top-of-mind for many people. One popular disinfection method that has been getting a lot of attention is ultraviolet sterilization. Given all the stress and anxiety, it may be tempting to purchase whatever you come across, but it is critical that you make an educated decision about what you purchase and how to use the product. Below, we'll go over 4 important aspects of UV-C disinfection.

1) Make sure you purchase the right wavelength

Not all ultraviolet light is the same, and the wavelength is what distinguishes UV lights that do and don't work for disinfection purposes. Ultraviolet is divided into three categories based on its wavelength value: UV-A, UV-B and UV-C. To date, the most direct and conclusive research on sterilization has shown that UV-C is the only category of UV wavelengths that consistently work for sterilization, as this wavelength range is the only range capable of direct DNA and RNA destruction. Several studies on particular viruses and microbes have been performed using UV-B and UV-A, but the mechanism under which disinfection occurs is less clear and conclusive.

Most of the UV "blacklights" that you see on the market emit in the UV-A wavelengths, and are therefore not effective for sterilization applications. Beware of products that simply use "ultraviolet" as a marketing term, as dishonest sellers may be taking advantage of unaware consumers by labelling their UV-A products as being "effective for sterilization", and perhaps citing smaller and narrow research studies performed on a particular virus strain to suggest that it would also be effective against all viruses, including the COVID-19 coronavirus. In contrast, UV-C has been shown to be effective against wide range of viruses such as avian flu, hepatitis A, herpes, influenza A, and polio, as well as coronaviruses.

It would be even better if the product you purchase provides the exact wavelength, in nanometers (abbreviated nm), at which the ultraviolet energy is emitted. This is because thymine and uracil, the nucleic acids in DNA and RNA, respectively, are susceptible to only a particular wavelength range that peaks at 265 nanometers. Therefore, products at or near 265 nanometers are typically the most ideal for sterilization. A common wavelength for UV-C LED products is 280 nanometers, but all else equal, this wavelength is less effective than 270 nanometers as it is farther from the 265 nanometer peak absorption wavelength.

For further reading on ultraviolet wavelengths for sterilization, see our introduction to UV-C here as well as our blog post on whether UV-C can kill coronaviruses.

2) Be aware of human, animal and material safety risks when using UV-C

UV-C wavelengths are far more powerful than other forms of ultraviolet. In fact, UV-C is not present in natural sunlight as it is blocked by earth's atmosphere. It is therefore very important to keep in mind that UV-C is an unnatural type of radiation, and that it more powerful than dangerous forms of UV radiation present in natural sunlight, namely UV-A and UV-B.

UV-C can cause sunburn in human skin and also lead to skin cancer. Never expose humans or animals to UV-C radiation. Because UV-C rays are invisible, there is an extra risk of unintended exposure. Therefore, when considering UV-C as a sterilization method, be very careful to install and configure the product in a way that prevents humans and animals from being exposed, and use protective gear if necessary. (For reference, it might help to get a sense of the risks by understanding that welders use protective equipment as the arc created also releases UV-C radiation).

While the immediate safety risks of UV-C are for humans and animals, UV-C is also damaging to certain materials. In a hospital, commercial or home setting, perhaps the most common material that would be susceptible to UV-C degradation would be plastic and wood. Different plastics would have different levels of resistance depending on whether or not they include UV stabilizers. There may be discoloration, weakening or the plastics may become brittle.

While the degradation may be only aesthetic in nature for some objects, some plastic objects may be completely compromised, leading to further safety risks. For example, if exposed for a long enough time, using UV-C to disinfect N95 masks may reduce its ability to properly filter out airborne pathogens.

On the other hand, metals have been shown to have high levels of UV-C resistance.

Also, be aware that plants are susceptible to UV-C radiation. If subject to too much UV-C, indoor houseplants may wilt and die as a result of excessive UV-C exposure.

Finally, we recommend considering total "dosage" when evaluating UV-C safety risks. In other words, you should consider not only the momentary power and intensity of the UV-C exposure, but also its duration, as a small intensity UV-C lamp, if exposed for an extended period of time, can be just as harmful as brief exposure to a high intensity UV-C lamp.

3) Understand the limitations of the UV-C lamp's ability to disinfect everything and everywhere

Be aware that UV-C lamps are not a magical device that will instantly and absolutely sterilize whatever room or area you place them in. For it to work properly, the UV-C radiation must reach a particular surface with sufficient strength. Some of the biggest pitfalls of UV-C sterilization include the inability to reach areas that are in "UV shadows." UV shadows refer to areas where another object blocks the UV rays from reaching.

As a simple example, let's say you're trying to use a UV-C lamp to disinfect your smartphone. Chances are, you will not be able to expose all sides of your smartphone simultaneously. You may want to flip your phone over a few times to make sure all sides receive enough UV-C exposure for sufficient disinfection.

Similarly, you are unlikely to be able to reach every nook and cranny of a room just be leaving a UV-C lamp on in the center of the room. Will you reach most surfaces? Perhaps, but you're likely to have missed quite a few spots where the UV-C just couldn't reach. As a simple rule of thumb, UV-C rays behave very much like regular light, and will not penetrate through most materials, and even clear materials like plastic and glass will not allow UV-C to pass through. A simple way to see what areas lie in the UV lamp's "UV shadow" might be to simply place a regular A-style light bulb in the location of the UV-C lamp, to visually observe which surfaces receive enough UV-C radiation.

This is where the form factor of a UV-C lamp becomes a significant point to consider. Traditional UV-C lamps are made in fluorecent tube style, which somewhat limits the UV-C ray distribution and angles. Recent developments have allowed for UV-C in LED form factors, and flexible UV-C LED strips, for example, can offer significantly more potential for innovation and versatility.

4) UV-C disinfection is not perfect: sterilization vs disinfection

You may have noted that in this blog post, we have somewhat used the terms sterilization and disinfection interchangeably. In strict technical terms, sterilization refers to the complete absence of any pathogens, while disinfection refers to the reduction of pathogens to the point where they are extremely unlikely to cause an infection. You may see alcohol wipes and other disinfectant products advertise 99.999% effectiveness, which refers to the fact that they may miss 0.001% of pathogens. As such, they are, strictly speaking, disinfectants, and not true sterilizers.

Likewise, be aware that UV-C is generally not capable of sterilization, and only capable of disinfection. UV-C is a very effective way to reduce the number of pathogens, but even if implemented and installed correctly, the end result can only be near-perfect at best. While UV-C may greatly reduce your risk of infection, to get as close as possible to true sterilization, it would be wise to have multiple lines of defense whenever possible.

For example, if you are concerned about pathogens on your smartphone, you may want to use disinfectant wipes first, and then use UV-C to further disinfect any areas that the cloth may have missed. Furthermore, even if you do everything you can to disinfect, you should not assume a surface is 100.0000% sterile after UV-C treatment.

Looking for a UV-C solution, or got more questions?

Waveform Lighting offers its cleanUV™ 270 nanometer UV-C products for disinfection applications. Please click here to learn more.