Hypoxic, dry, cold air is a stress to nasal air temperature conditioning (NATC) at high altitude, where humans often complain of nasal irritation. The vasodilator nitric oxide (NO) may modulate NATC (J Appl Physiol 87:1260, 1999). Hypoxic, dry (but not cold) air also reduces NO release into nasal air (Resp Physiol 114:285, 1998). Thus, we asked if simulated high altitude (normobaric hypoxic, dry air) would impair NATC. We infused (12 L/min) normobaric, hypoxic (100% N2), dry (0% humidity) air (21° C) or dry air (21° C, 21% O2, balance N2) into the nasal passages of seven adult humans. During breath holding, air entered the nose, passed around the soft palate, exited from the mouth and was collected for analysis of nasal NO release by chemiluminescence. NO output (nL/min) was calculated as the product of NO concentration and flow rate (timed collection measured in a Tissot gasometer). Nasal air temperatures were measured at one cm intervals from the nasal verge to a depth of 7 cm by thermocouples. Exponential curve fitting generated a half‐point value—the depth where nasal air reached half the difference between ambient and maximum cavity temperature. Half point depth increased during normobaric hypoxic, dry air infusion compared with dry air indicating impediment of NATC (see table). Nitric oxide release decreased during normobaric hypoxic, dry air infusion compared with compressed air. We confirm that nasal NO release is impaired by hypoxic, dry air and further suggest that, hypoxic air impedes NATC. Our findings are consistent with a role of NO in NATC and may help explain nasal irritation in humans at high altitude.NO output (nL/min)Half‐point (cm)(Supported by the Murdock Foundation).