Single-chamber fuel cells (SCFCs) are an alternative way to conventional SOFCs. Effectively, they do not require any more sealing between anodic and cathodic compartment's as the cell is fed with a mixture of hydrocarbon and oxygen. This paper deals with voltage oscillations observed with an SCFC composed of GDC (Ce_0.9Gd_0.1O_1.95) supported electrolyte, Ni-GDC anode and a BSCF (Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ) cathode, operating in the temperature range 500-600 °C and under various propane and oxygen mixtures, with a C₃H₈/O₂ ratio between 0.2 and 0.66. Electrical and Thermo-Programmed Oxidation (TPO) measurements combined with SEM observations allowed us proving that these oscillations are due to carbon nanowires deposition/oxidation cycles. A mechanism is proposed to explain this behavior.