Ventilation with outdoor air plays an important role influencing human exposures to indoor pollutants. This review and assessment indicates that increasing ventilation rates above currently adopted standards and guidelines should result in reduced prevalence of negative health outcomes. Building operators and designers should avoid low ventilation rates unless alternative effective measures, such as source control or air cleaning, are employed to limit indoor pollutant levels.

The olfactory test administered to patients at the Connecticut Chemosensory Clinical Research Center combines stability of outcome with sensitivity to variables known to affect olfaction (age, sex). The test, which pairs an odor threshold component with an odor identification component, readily resolves differences in function between patients and controls. It reveals differences in the distribution of functioning for various probable causes (nasal/sinus disease, postupper respiratory infection, and head trauma), proves sensitive to improvements in function caused by therapeutic intervention (ethmoidectomy, steroid administration for nasal/sinus disease), and correlates with objective signs of nasal/sinus disease (visual exam, x-ray). The two components of the test agree well, though the odor identification component seems somewhat more sensitive than the threshold component as currently designed.

Successful odor identification depends on (i) commonly encountered substances, (ii) a long-standing connection between an odor and its name, and (iii) aid in recalling the name. The absence of any one ingredient impairs performance dramatically, but the presence of all three permits ready identification of scores of substances, with performance seemingly limited only by the inherent confusability of the stimuli.

The investigation examined the association between the perceived identity of odorous stimuli and the ability to recognize the previous occurrence of them. The stimuli comprised 20 relatively familiar odorous objects such as chocolate, leather, popcorn, and soy sauce. Participants rated the familiarity of the odors and sought to identify them. At various intervals up to 7 days after initial inspection, the participants sought to recognize the odors among sets of distractor odors that included such items as soap, cloves, pipe tobacco, and so on. The recognition response entailed a confidence rating as to whether or not an item had appeared in the original set. At the time of testing, the participants also sought to identify the stimuli again. The results upheld previous findings of excellent initial recognition memory for environmentally relevant odors and slow forgetting. The results also uncovered, for the first time, a strong association between recognition memory and identifiability, rated familiarity, and the ability to use an odor label consistently at inspection and subsequent testing. Encodability seems to enhance rather than to permit recognizability. Even items identified incorrectly or inconsistently were recognized at levels above chance.

Inhaled vapours may stimulate both olfactory receptor cells and endings of the trigeminal nerve. The trigeminal nerve often contributes a pungent, irritating attribute to odours. Many odorants exhibit some pungency when dilute and most become pungent when concentrated. Because the trigeminal system commonly shares the chemosensory burden with olfaction, it is relevant to ask whether these anatomically distinct systems interact. Two obscure psychophysical observations argue for an inhibitory influence of trigeminal over olfactory activity. Katz and Talbert observed that a vapour with both odour and pungency might lose odour at high concentrations, irritation masking odour. The nineteenth century philosopher Alexander Bain, nothing that concentrated carbon dioxide (carbonic acid) evokes pungency, remarked "if a current of carbonic acid accompanies an odour, the effect (odour) is arrested" (ref. 8). We have taken up Bain's forgotten observation and used carbon dioxide to endow otherwise benign concentrations of odorant with varying degrees of pungency. The experiments reported here reveal a strong mutual interaction between pungency and odour, occurring without attenuation even when irritant enters one nostril and odorant the other.

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Detection thresholds were measured repeatedly for 11 chemicals in normosmic and anosmic subjects. The stimuli comprised the first eight members of the series of naliphatic alcohols, phenyl ethyl alcohol, pyridine, and menthol. Results showed that anosmics could detect, via pungency, all but phenyl ethyl alcohol reliably. In the aliphatic series, both odor and pungency thresholds declined with chain length in a way that implied dependence of both in part on phase distribution in the mucosa. Odor thresholds, however, declined more rapidly than pungency thresholds: the ratio of anosmics threshold/normosmics threshold increased from 23 for methanol to 10,000 for 1-octanol. The outcome of a scaling experiment employing normosmic subjects indicated that, with the exception of methanol and ethanol, pungency arose when perceived intensity reached a narrowly tuned criterion level. When thresholds were expressed as percentages of saturated vapor -an index of thermodynamic activity -thereby accounting for differences in solubility and in phase distribution in the mucosa among the various stimuli, both odor and pungency thresholds depicted a striking constancy across stimuli.

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