July 24, 2020

UV-C lights for Disinfection do not work as advertised

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I could use your help with something that is very important. Like many of you, I have used ultraviolet C (UV-C) lights for disinfection in my practice and have recommended them to friends and colleagues. I feel bad now, as I have found that many of these lights do not work as claimed, because they are the wrong spectrum of UV light. I am concerned that people using these lights will have a false sense of security. The lights need to be in the UV-C spectrum to be effective at killing bacteria and viruses, preferably with a wavelength of 250 – 270 nm.

UV-C lights are used for disinfection in a variety of ways including:

• UV-C lights used in a room to disinfect surfaces in the room
• UV-C lights used in air filtration systems to disinfect mold, bacteria, and viruses in the air
• Wand UV-C lights to disinfect packages and groceries
• UV-C units used to disinfect cell phones and small items

I purchased two 60 watt UV-C lights through amazon.com in March at $45 each but did not receive them until May. A colleague, Jim Wakefield, D.O., tested the lights for me using Petri dishes swabbed with household sample bacteria. He exposed half of the Petri dishes to the UV light for 60 minutes and the other half was kept as controls. After two days in an incubator, there was not much difference in bacterial growth in the Petri dishes exposed to the UV light compared to the controls.

This showed that the lights I purchased were useless for disinfection. Unfortunately, I was unable to return them for a refund as the deadline for returning them had already passed. It also would have been expensive to return them to the company that manufactured them in China. These lights are no longer listed on amazon.com, so I was not able to leave a review.

This is the $45 “UV-C Light”
that failed the tests.

The lights that I purchased look identical to the one in this article.

We did another test with a 100 watt LED UV-C light with the same failing results. The 100 watt LED was also purchased on Amazon.

I see many websites selling UV lights that tout the disinfecting benefits of UV-C light, but they do not specifically state that their lights emit light in the effective UV-C range. In order to properly disinfect, the lights should emit light with wavelengths in the range of 200 – 280 nm. The optimal wavelength for disinfection is 265 nm. I do not trust the websites that do not include this specific information about their products. When purchasing a UV-C light you may wish to ask about the return policy in case it does not test as being effective.

Here is an easy way to test your UV-C light

I recently found some tests for UV-C lights that are much faster and easier to perform than using Petri dishes and an incubator. The tests use reusable plastic cards with an area that changes color when exposed to UV-C light. I know these cards work because they show the same results that we got from the test with the Petri dishes.

You can find the reusable UV-C detection test cards on Amazon. https://www.amazon.com/gp/product/B088TSB1BF/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&psc=1

Here is another source for UV-C detection test cards that I found. This card tests for UV-A and B, and UV-C light between 250 and 270 nm. I ordered this card on July 23 and received it three weeks later on Aug. 13.

UV-C Lights that work

I found a 95-watt complete room and surface sterilizer for $389.99 that passed both tests, using the Petri dishes and the UV-C detection card. My $45 UV lights did not pass either test.

https://www.cureuv.com/collections/room-sterilizers/products/deluxe-germawayuv-95-watt-uv-c-surface-sterilizer

My colleague tested this light using Petri dishes seeded with bacteria and found steadily decreasing levels of bacteria when exposing the plates to the lights for 5, 10, 15 or 20 minutes. There was still some bacteria after 20 minutes, so exposure of the surface to the UV-C light for 1 hour would be better.

If you are using a UV-C light to disinfect surfaces, be aware that it will only disinfect the areas that the light reaches. If there are irregularities on the surface it may not be as effective. I recommend using a disinfectant spray or wipes in addition to the UV-C light for disinfecting surfaces.

This light is expensive, so I am looking for other lights that may work as well. I will list other UV-C lights in the comments below.

Here is how you can help

I am looking for less expensive UV-C lights that will also pass the test. If you have already purchased a UV-C light, please buy one of the test cards (only $5.99) and test your light, then use the comment section in this blog to report the results of your test.

If you are not a member of massagelibrary.com you may not be able to post a comment to this blog. In that case please email your comment to me at jmally@massagelibrary.com and I will post it.

When you test your light, please test it with the card at different distances from the light so we can learn the range of effectiveness of the light. Please include the name and model of the UV-C light and the link of where to purchase it.

Bookmark this blog page so you can review the comments and make more informed choices when purchasing UV-C lights.

Caution

UV-C light can be damaging to the eyes and the skin. Use UV glasses or goggles when testing the light or leave the room. Many of the lights have remote controls and timers or have a delay when you turn them on so that you can leave the room. Also, prolonged exposure of UV light may degrade colors in paintings and artwork. I have a painting in my office that I cover with a towel when using the UV-C light.

If you are using a UV-C light to disinfect surfaces, be aware that it will only disinfect the areas that the light reaches. If there are irregularities on the surface it may not be as effective. I recommend using a disinfectant spray or wipes in addition to the UV-C light for disinfecting surfaces.

Disclaimer

I have no financial interest in any of the products I refer to in this blog post and do not receive any compensation for recommending them.

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