Using flow-olfactometer for chemosensory event related brain potentials (CSERP) the air escapes the contralateral nostril from the stimulated nostril via the nasopharynx. Theoretically, the escaping odorous airflow is able to stimulate the contralateral chemosensory receptors and might activate the olfactory or the trigeminal brain processes. Testing 18 healthy subjects, we were able to show that it was possible to generate CSERP by strictly monorhinal stimulation with closed contralateral nostril. That means that the rectangular shapes of the brief chemosensory stimuli were not disturbed. The latencies of N1 and P2 and the amplitudes (N1P2) of CSERP (stimulants: H2S and CO2) were not different with either open or closed contralateral nostril. The induced CSERP were independent of stimulated nostril side. Additionally we found that with closed contralateral nostril more than 90% of passive monorhinal chemosensory stimuli were perceived. In further imaging studies the presented paradigm should be applied with strictly monorhinal stimulation to investigate the chemosensory processing pathways with high time resolution (EEG/MEG).