In this work, we confirmed the negligible influence of grain size on the gas-sensing capabilities of p-type semiconducting chemiresistive oxide gas sensors. For this purpose, p-type NiO nanofibers were synthesized by the electrospinning technique, and their sensing properties were investigated in terms of CO and NO2 (representative reducing and oxidizing gases, respectively) response, particularly as a function of the size of the nanograins existing in individual nanofibers. The size of the nanograins influenced the CO and NO2 response of the NiO nanofibers to only a small extent, in sharp contrast to its prominent influence on the sensor response of n-type semiconducting chemiresistive oxide gas sensors. The results not only confirm the established knowledge, but also provide a useful guideline for the fabrication of p-type oxide nanofiber-based chemical sensors. (C) 2015 Elsevier B.V. All rights reserved.