UV-C Banana Test from UVClean House on Vimeo.
Watch this video to see how you can perform a DIY UV-C verification test.
The longer (and closer) the exposure of the source UV-C light to the subject matter (in this case, the banana peel) the easier we can decipher the effect of UV-C.
In some cases, a delayed response time of up to 16 hours is needed to render a visible color discoloration in the banana peel's skin where the UV-C light was directed. The single layer of black masking/electrical tape on adjacent areas is impermeable to the UV-C light to demarcate where the UV-C light does NOT affect as a control comparison to areas with and without UV-C light exposure.