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UVCTest: What Exposure Durations Can Be Recommended for UVC Testing?

UVC Disinfection Robot UVCTEST Device
UVC Disinfection Robot and UVCTest Device

UVC Testing and the Appropriate Test Duration

In an earlier post, we discussed the UVCTest™ product durability testing capabilities and how it was developed following the common use of disinfection tools based on 254 nm UVC radiation. We saw that all kinds of materials may degrade much faster than expected when exposed to this new stress.

In this post, we will discuss the matter of estimating the appropriate test duration for UVC exposure testing. We will also introduce the Atlas UVCTest Duration Calculator, which we previously promised to develop.

Atlas UVCTest Duration Calculator

Material testing with UVC is in its infancy and recommended test durations are limited or even illogical. Yet one of the most frequent questions is: how long should I test?

When we started to think about the best way to estimate appropriate UVCTest durations, we came up with six essential questions:

• What is the UVC dosage per application (which can vary by the UVC sterilization device used)?
• How many times per week are UVC disinfection routines done?
• What is the expected service life of the tested product?
• What is the planned irradiance level (mW/cm2) for UVC testing?
• How long is a “light” phase?
• Will you include a dark phase following the “light” phase? If yes, how long is the dark phase?

With the answers to the questions above, it then becomes easier to calculate a starting point for test durations.

The Atlas UVCTest Duration Calculator provides six entry fields highlighted in yellow which correspond to the questions listed above. Three result fields highlighted in purple show you the accumulated UVC exposure, the UVCTest exposure duration (light time), and the total test duration (with/without dark phase).

The benefit of the Calculator is to establish a starting point for your UVC test duration. To be clear, the calculator makes no assumption of material specific responses to UVC exposure. Therefore, no guarantees can be made that these calculated durations will accurately predict service life. However, by validating and comparing results of your accelerated UVC test to natural exposures, you can apply adjustments and gain further insights into the actual acceleration of your test and correlation to reality.

UVC Disinfection Robot and UVCTest Device
UVCTest Duration Calculator: 144.4 h at 7.0 mW/cm2, incl. dark phase; simulating 7 disinfection applications/week over 5 years

Test Temperatures and Dark Phases

Now that we have established a method to determine the test duration, let us consider test temperature. One reference for UVC testing including recommendations for black standard temperature is IEC 60335-1(2020), Annex T titled “UV-C radiation effects on non-metallic materials”. The test method recommends a Black Panel temperature setting of 63 °C ±3 °C. This value appears to be too high for simulating surface temperatures, since UVC disinfection applications typically occur indoors at much lower ambient temperatures. Therefore, we think appropriate Black Panel temperature conditions may range between 30-40 °C.

When running the UVCTest at irradiance levels at or near the low end of the range 2.0 – 7.5 mW/cm2, the above mentioned Black Panel temperatures around 30 °C can be controlled.

Finally, some thoughts on dark phases. When performing testing services for our customers, we have noted that we can categorize them as those that insist on dark phases and others that wish to avoid them. For some polymers, dark phases can help to increase correlation to real world degradation as continuous irradiation can cause saturation effects. Radiation-induced degradation processes within such polymers require relaxation time (dark phases) to be fully effective—this is known as actinic effects. For other materials not requiring relaxation times, there is of course the advantage of shorter test durations.

More Information

Download free UVCTest Duration Calculator

Take a deeper dive into materials durability testing against UVC radiation and listen to our free recorded Atlas Online Seminar or download a free Application Guide.