Abstract Copper oxide (CuO) nanofibres are utilised to sense the toxic and abrasive gas hydrogen sulfide (H₂S) in the ppm (parts per million) range. The detection by CuO is based on a significant increase in the conductance upon the formation of CuS, and is thereby selective and sensitive towards H₂S. Nanofibres outperform thin films of CuO by compensating the volumetric stress which occurs during sensing. Here, sensors are presented exhibiting up to 600 cycles of sensing and regeneration. To get further insights into the degradation of the fibres upon the reaction with H₂S the sensors were analysed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), resistance and linear sweep voltammetry (LSV) measurements before and after cycling. SEM and TEM revealed a drastic change in morphology of the CuO fibres resulting in an undefined aggregate of nanoparticles after 600 cycles. Resistance and LSV measurements showed that the contacting and the measurement process itself are crucial factors for optimising long-term use of CuO-based H₂S sensors.