We conducted light irradiation experiments in air to clarify influence of atmosphere on the operation of a photo-assisted atomic switch. In air, Pt-Ag2S/Ag nanogap electrodes with a PTCDI thin layer in their nanogaps showed current fluctuations with an applied bias of from 1.5 V to 6 V regardless of the bias polarity and with or without light irradiation. This is in contrast to the fact that only two things cause an increase in current that result in the formation of a silver bridge and switching behavior under vacuum, namely, light irradiation and the application of positive bias to the Ag 2S/Ag electrode . In addition, photocurrent caused by irradiating a PTCDI thin layer was found to be sensitive to air and to N2. These results indicate that moisture or other gas molecules in air and in N 2 have an influence on the photo-assisted atomic switching behavior.