Hidden hardware degradation can silently undermine the reliability of scientific experiments across disciplines. Instruments that appear to function normally may, in fact, produce systematically distorted results for months or years, affecting research precision and data reproducibility. In this study, we identify and analyze a previously unrecognized source of experimental error: gradual and uneven aging of high‐power light‐emitting diodes (LEDs) used in photochemical equipment. Although the efficiency loss of LEDs is known in engineering, their unpredictable and uneven degradation has not been recognized as a cause of error in chemical experiments. To detect and quantify this effect, we developed a multidisciplinary diagnostic framework combining seven complementary methods: three quantitative measurements (photodiode readout, graphite calorimetry, and ferrioxalate actinometry), two reaction‐based methods (Paternò–Büchi cycloaddition, photocatalytic aryl bromide reduction), and two visual assays (phenothiazine photochromism, and a nickel–thiolate ‘photoclock' system). Together, these approaches revealed gradual declines in LED performance, leading to significant nonuniformity in light output and reaction yields. These findings demonstrate that unnoticed hardware aging can compromise reproducibility even in well‐controlled laboratories, emphasizing the need for regular diagnostics in modern photochemical and automated systems. In addition to photochemistry, this framework exemplifies a general strategy for improving the precision, traceability, and long‐term reliability of experimental measurements.
Kozlov et al. (Sun,) studied this question.
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