Perceived Odor Intensity Research Articles

Olfaction modulates cortical arousal independent of perceived odor intensity and pleasantness

Throughout history, various odors have been harnessed to invigorate or relax the mind. The mechanisms underlying odors’ diverse arousal effects remain poorly understood. We conducted five experiments (184 participants) to investigate this issue, using pupillometry, electroencephalography, and the attentional blink paradigm, which exemplifies the limit in attentional capacity. Results demonstrated that exposure to citral, compared to vanillin, enlarged pupil size, reduced resting-state alpha oscillations and alpha network efficiency, augmented beta-gamma oscillations, and enhanced the coordination between parietal alpha and frontal beta-gamma activities. In parallel, it attenuated the attentional blink effect. These effects were observed despite citral and vanillin being comparable in perceived odor intensity, pleasantness, and nasal pungency, and were unlikely driven by semantic biases. Our findings reveal that odors differentially alter the small-worldness of brain network architecture, and thereby brain state and arousal. Furthermore, they establish arousal as a unique dimension in olfactory space, distinct from intensity and pleasantness.

Field and intervention study on indoor environment in professional classrooms

To study the variation of environment in the professional classroom during lecture hours, multiple field experiments and intervention experiments on indoor and outdoor temperatures were conducted in a university professional classroom in Shaoxing during the spring. Environmental data, including indoor and outdoor temperatures, relative, and CO2 concentrations, were recorded every 5 min. Volatile organic compounds (VOC) were sampled, and indoor air quality was evaluated repeatedly. Results showed that the classroom’s average indoor air temperature ranged from 17.8–29.2 ℃, the average indoor relative humidity from 34.5%–91.0%, the average CO2 concentrations from 921.6–1805.2 ppmv, and total VOC concentrations from 330–682 ppbm. The subjective evaluation conducted during the intervention experiments indicated a significant increase in perceived odor intensity upon entering the classroom. When the CO2 concentration reached 2000 ppmv, the satisfaction and acceptability of the air quality for the subjects and invitees decreased significantly. In the temperature range of 17–31 ℃, the CO2 emission rate of human body was estimated to increase by 0.78 L/h for every 1 ℃ increase in temperature. To maintain the indoor CO2 concentration at 1000 ppmv, the required ventilation rate for each person must be increased by 0.25 ± 0.3 L/s.

Children's odor pleasantness ratings may not differ according to pubertal status: Preliminary results from a sample of 11–14-year-old Czech children

Puberty tends to be viewed as a “turning point” in hedonic perception of body odor (BO)-related smells. The pubertal stage, a potential proxy for the underlying physiological changes, may contribute to variation in odor hedonic perception. Other potential modulators of odor hedonics are general semantic knowledge about odors (which also tends to be subsumed under the term “age”) and perceived odor intensity. The present cross-sectional study examined differences in hedonic odor perception across puberty in 205 Czech children aged 11–14 (89 boys). We investigated whether children differ in the hedonic appraisal of BO-related (16-androstenes and castoreum control), but also food and non-food odors according to their pubertal (penis/breast and pubic hair) development and general semantic knowledge about odors (operationalized as odor identification), controlling for age and perceived odor intensity. As a subsidiary aim, we examined variation in odor identification. We asked the children to self-stage themselves using drawings depicting Tanner's penis/breast and pubic hair stages of pubertal development, estimated their general semantic knowledge about odors with a Sniffin’ Sticks identification test, and obtained their pleasantness and intensity ratings of body odor-related, food, a non-food smells. We found that the participants’ ratings of the 16-androstenes and those of the perceptually similar odor of castoreum differed according to perceived intensity and, in the latter case, in boys vs. girls as well, but there were no influences of pubertal status or odor identification on the perceived pleasantness. Similarly, hedonic appraisal of non-food (but not food) odors was only influenced by perceived intensity. Regarding odor identification, differences between boys and girls were limited to younger children and did not become more marked throughout puberty. Perceived pleasantness of odors, irrespective of whether they are associated with body smells, food, or other, does not appear to vary across puberty, and boys and girls seem to achieve similar levels of semantic odor knowledge as they grow up.

Differences in olfactory functioning: The role of personality and gender

AbstractThis study aimed to investigate the relationship between the gender and personality traits of individuals and their ability to detect, identify, and discriminate odors. The dataset on olfactory performance was compiled from a panel of 207 healthy human volunteers. The dataset for the odor identification test was collected using a set of 10 distinct odorants, and the odor discrimination test dataset was collected using a well‐established “Sniffin sticks” (Burghardt®, Wedel, Germany) odor discrimination test kit. To assess the Big Five personality traits of study participants, a self‐report survey questionnaire based on the International Personality Item Pool‐Neuroticism, Extraversion, and Openness (IPIP‐NEO) was used. Here, we conducted a statistical analysis to investigate the role of personality measures and gender on olfactory performance, as well as the relationship between olfactory performance and perceived odor intensity, pleasantness, and familiarity. The findings of the study suggest the existence of some relationships between gender and personality traits and odor discrimination and identification, but not odor detection. Conscientiousness and openness to experience personality traits were positively correlated with odor identification, while agreeableness and conscientiousness personality traits were positively correlated with odor discrimination. The extroversion personality scale was negatively correlated with odor discrimination. Additionally, male participants performed better than females in odor identification tasks, while females performed better in odor discrimination. The neuroticism personality domain was associated with odor identification tasks in males but not in females when analyzed separately. Correct identification of odors was also associated with their perceived familiarity.Practical ApplicationsThe results of this study may have important practical implications for a range of industries, including the fragrance and food industries. These findings may help tailor products to specific consumer preferences based on personality and gender, enhancing product appeal. Further, the fragrance and food industries can develop targeted marketing campaigns using fragrances and flavors associated with particular personality types or genders. Similarly, product testing can also be improved by representing a diverse range of personality types and genders to obtain more accurate feedback. The study insights can further guide the development of flavor and taste pairings that resonate with specific personality and gender groups. Overall, by considering olfactory differences related to personality and gender, the fragrance and food industries can segment their target markets more effectively and design products that appeal to different consumer groups.

Evaluation of the intensity of cigarette odors based on the perception of consumers.

We evaluated the tobacco odor intensity of cigarettes based on a large consumer panel and explored the differences of odor intensity perception based on sex, age and smoking habits. The perceived intensity of tobacco odor of cigarettes was evaluated using a consumer group method. A consumer panel of 240 volunteers (80 smokers, 80 ex-smokers and 80 non-smokers) was asked to smell eleven unlit cigarettes and then report their tobacco odor intensity in a specific questionnaire. All volunteers clearly determined the presence of tobacco odor in all cigarettes. There is a general decrease of the perceived odor intensity with age, for both males and females. Moreover, tobacco odor perceived intensity, among all volunteer groups (smokers, non-smokers, ex-smokers), was higher for females than for males. Non-smokers declared the highest perceived tobacco odor intensities, followed by ex-smokers and smokers, who recorded the lowest perceived odor intensity. Perceived odor intensity decreased with age, with a higher rate for females compared to males, but independently of the smoking habits. Regular and untrained consumers confirmed that a tobacco odor of different intensity can be perceived during the smelling of unlit cigarettes. This perceived intensity depends on sex, age and smoking habits.

The effect of perceived odour edibility induced via conditioning on olfactory habituation

Previous research shows that edibility (top-down feature) could modulate olfactory habituation, as habituation follows a different trend for food or non-food odours. However, the impact of bottom-up features of the stimuli (e.g., trigeminality) cannot be ruled out. To minimize such influences, in the present experiment, forty-four participants completed a habituation paradigm while being presented with the same odour (i.e., vanilla) that could be associated both to food and non-food stimuli. In the conditioning phase, participants were exposed to the vanilla odour coupled either with food (edible group) or with non-food pictures (non-edible group). The conditioning protocol affected the perceived edibility of the vanilla odour, namely the edible group rated the odour significantly more edible than the non-edible group. In the habituation phase, participants were exposed to the same vanilla odour in a block of 20 trials. They rated the perceived odour intensity and pleasantness after each trial. Linear mixed-effects models showed that the odour intensity decreased over time only in the non-edible group. While the pleasantness decreased in both groups. Our findings show that, when minimizing the influence of other possible olfactory features (e.g., trigeminality, pleasantness), odour edibility modulates olfactory habituation.

Appetite-regulating hormones modulate odor perception and odor-evoked activity in hypothalamus and olfactory cortices.

Odors guide food seeking, and food intake modulates olfactory function. This interaction is mediated by appetite-regulating hormones like ghrelin, insulin, and leptin, which alter activity in the rodent olfactory bulb, but their effects on downstream olfactory cortices have not yet been established in humans. The olfactory tract connects the olfactory bulb to the cortex through 3 main striae, terminating in the piriform cortex (PirC), amygdala (AMY), olfactory tubercule (OT), and anterior olfactory nucleus (AON). Here, we test the hypothesis that appetite-regulating hormones modulate olfactory processing in the endpoints of the olfactory tract and the hypothalamus. We collected odor-evoked functional magnetic resonance imaging (fMRI) responses and plasma levels of ghrelin, insulin, and leptin from human subjects (n = 25) after a standardized meal. We found that a hormonal composite measure, capturing variance relating positively to insulin and negatively to ghrelin, correlated inversely with odor intensity ratings and fMRI responses to odorized vs. clean air in the hypothalamus, OT, and AON. No significant correlations were found with activity in PirC or AMY, the endpoints of the lateral stria. Exploratory whole-brain analyses revealed significant correlations near the diagonal band of Broca and parahippocampal gyrus. These results demonstrate that high (low) blood plasma concentrations of insulin (ghrelin) decrease perceived odor intensity and odor-evoked activity in the cortical targets of the medial and intermediate striae of the olfactory tract, as well as the hypothalamus. These findings expand our understanding of the cortical mechanisms by which metabolic hormones in humans modulate olfactory processing after a meal.

Association of indoor temperature and air quality in classrooms based on field and intervention measurements

To investigate the variation of classroom environment during typical lecture hours, repeated field measurements and intervention experiments for indoor temperature were carried out in a typical class (95 min in duration, 0.32–0.39 person/m2 of occupants density) in a spring semester of a university in Beijing. Environmental data were recorded every 5 min, including indoor temperature, relative humidity and carbon dioxide (CO2) concentration. Additionally, volatile organic compounds (VOCs) were sampled and indoor air quality (IAQ) were evaluated repeatedly. The results of field measurements showed the average air temperature in the classroom ranged from 21.2 ± 0.8 °C to 26.8 ± 0.7 °C, relative humidity ranged from 23.1 ± 1.8% to 57.5 ± 0.2%, and the average concentrations of CO2 and total volatile organic compounds (TVOC) were 1,291–1,833 ppmv and 159-1,178 ppbm respectively. The subjective evaluations collected during intervention experiments showed that perceived odor intensity by visitors upon entering the room increased significantly, meanwhile the satisfaction and acceptability of air quality reduced considerably at the indoor temperature of 27 °C than that at 24 °C. Present results suggest when the indoor temperature rises, it is necessary to increase the outdoor air supply rate to ensure air freshness in classrooms. Subsequently, the calculated CO2 emission rate by students increased by 0.54 L/h per person for every 1 °C rise in indoor temperature. Corresponding to the control target of indoor CO2 concentration of 1,000 ppmv, the outdoor air ventilation rate required to eliminate occupant-generated pollution needs to be increased by 0.25 L/s per person.

Gender difference in ratings of odor intensity during olfactory training

AbstractThis study aimed to elucidate the role of smell diaries in Olfactory training (OT) and probe gender differences in intensity ratings and measured olfactory function throughout the OT course. Fifty olfactory loss patients (36 women and 14 men) undergoing OT rated odor intensities on a daily basis for at least 12 weeks. They exhibited significant improvement in measured olfactory function after OT; gender had no significant effect. As for the diaries, women rated odors with higher intensities than men, and ratings from women increased with time while men rated odors at the same level. Across all patients, there was a weak positive correlation between ratings and psychophysical test scores (r = 0.30, p = .04). Throughout the OT course, the increase in odor intensity ratings was more pronounced in women than it was in men (F[1, 44] = 7.9, p = .007). However, this gender‐related difference was not found for measured olfactory function, suggesting pronounced gender‐differentiated behaviors in terms of self‐ratings of olfactory function.Practical ApplicationsOT is often used for the rehabilitation of olfactory loss, and a smell diary is suggested to document the perceived odor intensity. The patients can benefit from this rating procedure by surveying the olfactory change, predicting their OT outcomes, and motivating them to maintain training. Our study provides evidence that each gender rates odor intensity in different ways; therefore, the rating scores should be interpreted correspondingly. It also implied that women among well‐trained sensory panelists (e.g., for food quality control) could rate the intensity of stimuli higher than men in the same panel. The rating bias arising from gender should be taken into consideration when it comes to professional sensory evaluation.

Olfactory habituation to food and nonfood odours.

Olfactory perception can be modulated by the repeated exposure to odours. Olfactory habituation is a reduced behavioural response to repetitive stimulation. Edibility is considered an important top-down feature that can affect olfactory perception, but whether it could modulate olfactory habituation when food or nonfood odours are repeatedly smelled remains unclear. Indeed, due to their ecological salience, food odours attract attention automatically which might slow down habituation. This registered report aimed to determine whether olfactory habituation shows a different pattern when participants are presented with food or nonfood odours. In a within-subject design, 50 participants were tested under satiated and fasted states in separated experimental sessions. In each session, participants were exposed to the same food and nonfood odour in different blocks of 20 trials each. Participants rated the perceived odour intensity and pleasantness after each trial. We used an intermittent odour presentation to reduce olfactory fatigue while capitalising on the effect of cognitive states on habituation. Linear mixed-effects models showed that the perceived odour intensity decreased over time only for nonfood odours. Conversely, the perceived odour pleasantness decreased significantly more across trials for food odours. These effects were retrieved regardless of the participant's hunger state. Our results are in line with the olfactory-specific satiety theory which posits a specific decrease in the perceived pleasantness of food odours, without changes in the perceived odour intensity. In short, our findings indicate that perceived odour edibility modulates olfactory habituation, extending the previous literature on the impact of top-down factors on olfactory perception.

Olfactory discrimination of fat content in milks is facilitated by differences in volatile compound composition rather than odor intensity

The mechanisms underlying the ability of humans to olfactorily discriminate fat content in milks remain unknown. In this study, we found that fat contents (0.5, 1.5 and 3.5% fat) can be discriminated by olfaction in commercially available pasteurized milks (p < 0.05) but not in ultra-high temperature processed (UHT) milks. The composition of volatile compounds of pasteurized milks differed with fat content, whereas that of UHT milks differing in fat content was similar. Principal component analysis revealed that differences in volatile compound composition of pasteurized milks differing in fat content contribute to olfactory discrimination. In UHT milks, acetoin and 2-heptanone may mask odor differences leading to indistinguishable odors. No differences were observed regarding perceived odor intensity of pasteurized milks or UHT milks differing in fat content. We conclude that the olfactory discrimination of fat content in pasteurized milks is facilitated by differences in volatile compound composition rather than odor intensity.

Effect of Olfactory Stimulation with Vanilla Odor on Degree of Gastric Myoelectrical Activity

Olfactory stimulation elicits various physiological responses. However, few reports exist on the changes in gastric motility during olfactory stimulation in humans. In this regard, we carried out electrogastrography (EGG) to non-invasively measure the gastric myoelectrical activity, which regulates gastric motility. Moreover, subjective sensory evaluation was performed to determine which characteristics of vanilla odor at two different concentrations affect the myoelectrical activity. The participants consisted of eight healthy young males. EGG and electrocardiography (ECG) recordings were obtained approximately 20 min prior to and during olfactory stimulation. Autonomic nervous system activity was evaluated in terms of heart rate variability (HRV) and mean heart rate (HR) from ECG signals. EGG signals were analyzed by spectral analysis. In addition, the translation error was estimated by the Wayland algorithm. Sensory evaluation was performed using the Visual Analog Scale (VAS). There were no significant differences in HRV and HR values and results of spectral analyses of EGG signals in all sample presentations. The translation error of EGG signals and the rating of perceived odor intensity significantly increased in a concentration-dependent manner. There was a strong positive correlation between translation error and odor intensity. The correlation found between translation error and odor intensity suggests that the higher the vanilla odor intensity was perceived, the greater the randomness of EGG signals was. Our results suggest that the application of the Wayland algorithm to EGG signals can be used as an objective indicator in odor evaluation.

Differences in olfactory habituation between orthonasal and retronasal pathways

The odorant arrives at nasal olfactory epithelium ortho- and retronasally. This experiment aimed to study the potential different olfactory habituation in orthonasal and retronasal pathways. 68 subjects were stimulated by constant airflow with an odor (50% phenethyl alcohol, PEA or 5% n-butyl acetate, BA) presented ortho- or retronasally. Participants rated the perceived odor intensity (0–10 points) per minute until the odor sensation disappeared. We also investigated the cross-habituation: when the subjects achieved full habituation, continue to rate odor intensity in a different pathway after instantly switching the odor stimulation pathway. The olfactory habituation curve was drawn. The differences of ratings between the orthonasal and retronasal olfaction at different time points and between male and female subjects were analyzed. The two odor intensity ratings decreased as the time extended, share the same “fast followed by slow” type. The ratings of orthonasal olfaction decreased faster than that of retronasal. The intensity rating of PEA of male retronasal approach was lower than that of female at the 5th min (p = 0.018). When orthonasal full habituation achieved, there was significant difference between the intensity ratings and the initial ratings of the retronasal stimulation pathway (p < 0.0001), and vice versa. We found obvious habituation as well as cross-habituation in both orthonasal and retronasal olfaction. The habituation of orthonasal olfaction was faster than that of retronasal olfaction. These different habituations were related to the gender.

Chemical Composition and Sensory Evaluation of Saffron.

The quality and economic value of saffron, one of the most counterfeited spices, are based on three key substances that are relatively easy to measure: crocines (colour); picrocrocines (bitter); safranal (odour impact). Despite being well-known, as their concentration is correlated to sensory intensity, a detailed sensory evaluation, performed by a trained panel, supported by advanced analytical approaches, may better show the relationships between saffron composition and sensory perception. Three saffron samples of different Italian origins (Sardinia and Tuscany) were evaluated by a trained sensory panel and their chemical composition was determined by HPLC (High Performance Liquid Chromatography) and spectrophotometry. Safranal concentration and the perceived odour intensity were positively correlated while relationships between picrocrocine and bitter perception were more complex to detect. By correlating (Multiple Factor Analysis) saffron sensorial and chemical profiles, this work aims at improving saffron characterisation while providing better information on the quality of this valuable spice.

The Effect of an Active Plant-Based System on Perceived Air Pollution.

Active plant-based systems are emerging technologies that aim to improve indoor air quality (IAQ). A person’s olfactory system is able to recognize the perceived odor intensity of various materials relatively well, and in many cases, the nose seems to be a better perceiver of pollutants than some equipment is. The aim of this study was to assess the odor coming out of two different test chambers in the SenseLab, where the participants were asked to evaluate blindly the level of acceptability, intensity, odor recognition, and preference at individual level with their noses. Two chambers were furnished with the same amount of new flooring material, and one of the chambers, Chamber A, also included an active plant-based system. The results showed that in general, the level of odor intensity was lower in Chamber B than in Chamber A, the level of acceptability was lower in Chamber A than in Chamber B, and the participants identified similar sources in both chambers. Finally, the preference was slightly higher for Chamber B over Chamber A. When people do not see the interior details of a room and have to rely on olfactory perception, they prefer a room without plants.

Electrical stimulation of the medial orbitofrontal cortex in humans elicits pleasant olfactory perceptions

BackgroundOlfactory hallucinations can be part of epileptic seizures of orbitofrontal origin. Olfactory hallucinations, however, are rare and therefore the semiology, localization and lateralization characteristics are underdetermined. In addition, many discrepancies are found in the literature regarding olfactory processing and orbitofrontal (OF) functions and olfactory function. Particularly, the questions of laterality and affective component in coding of odors in the OF cortex remain controversial. AimsThis study explored whether cortical electrical stimulation of the OF and mesiotemporal brain can trigger olfactory hallucinations with special focus on olfactory percepts in terms of laterality and hedonics. Materials and methodsEight patients with temporal lobe epilepsy participated in the study, at the time of invasive exploration of their epilepsy. The most distal contact of the OF and anterior hippocampus depth electrodes were stimulated (50 Hz, 0.2 ms biphasic pulse; maximal stimulation 4 mA). Patients were instructed to report any kind of sensation they might experience. Intracranial depth electrodes were localized (iElectrodes): subject-specific brain mask, subcortical segmentation and cortical parcellation based on the Destrieux atlas (FreeSurfer) were superposed to the coregistered T1-weighted MRI and CT images (SPM). The center of mass of each electrode-artifact cluster determined the electrode localization. The electrode labeling was done in patient space. To obtain the electrode coordinates in Montreal Neurological Institute (MNI) space, the images obtained previously in the patient space were first segmented and normalized (SPM). Then, the localization procedure (iElectrodes) was run again with these new normalized images in MNI space. ResultsNo hallucination was evoked by stimulation, neither of the right nor the left hippocampus (8/8 patients). Pleasant olfactory hallucinations were evoked by OF stimulation in 5/8 patients in either hemisphere. Patients named the percept as the smell of lemon or coffee for example. Among those 5 patients, electrodes were localized in the cortex of the olfactory sulcus, medial orbital sulcus or medial OF gyrus. Increasing stimulation amplitude changed the olfactory percept identification in 3 out of those 5 patients. No affective judgement or change in perceived odor intensity was reported by the patients. No hallucination was evoked by the stimulation of the white matter of the medial OF brain in 3/8 patients independently of the hemisphere stimulated. ConclusionsThis study demonstrated that stimulation of the cortex of the medial OF brain and not of its white matter elicits specific pleasant olfactory hallucinations independently of the hemisphere stimulated, supporting one symmetrical olfactory processing in human.

Engineered Polymersomes for the Treatment of Fish Odor Syndrome: A First Randomized Double Blind Olfactory Study.

Trimethylamine (TMA) is a metabolite overtly present in patients suffering from trimethylaminuria (TMAU), a rare genetic disorder characterized by a strong “fishy” body odor. To date, no approved pharmacological treatment to sequester excess TMA on the skin of patients exists. Here, transmembrane pH gradient poly(isoprene)‐block‐poly(ethylene glycol) (PI‐b‐PEG) polymersomes are investigated for the topical removal of TMA. PI‐b‐PEG amphiphiles of varying chain length are synthesized and evaluated for their ability to form vesicular structures in aqueous media. The optimization of the PI/PEG ratio of transmembrane pH gradient polymersomes allows for the rapid and efficient capture of TMA both in solution and after incorporation into a topical hydrogel matrix at the pH of the skin. A subsequent double blind olfactory study reveals a significant decrease in perceived odor intensity after application of the polymersome‐based formulation on artificial skin substrates that has been incubated in TMA‐containing medium. This simple and novel approach has the potential to ease the burden of people suffering from TMAU.

Frequent minty chewing gum use is associated with increased trigeminal sensitivity: An fMRI study

Repeated sensory exposure through frequent consumption of certain foods leads to changes in the processing of sensory cues. We investigated the influence of frequent minty chewing gum consumption on the neurobehavioral processing of intranasal trigeminal and olfactory stimuli. fMRI responses to a trigeminal minty odor (L-menthol), a non-trigeminal minty odor (L-carvone), and a non-trigeminal non-minty odor (strawberry) were assessed in 29 young adults (mean age = 23 years, SD = 4.3 years; mean BMI = 22.7, SD = 1.9; thirteen females), who were divided into a minty chewing gum high frequency (N = 18) and a low infrequency (N = 11) groups based on their self-reported frequency of chewing gum consumption. Participants’ performance for odor lateralization, ratings for perceived odor intensity, pleasantness, familiarity, and pungency were also collected. Compared to the low frequency group, the high frequency group rated L-menthol as more familiar and performed better during the L-menthol lateralization test. The high frequency group compared to low frequency group showed stronger activation in trigeminal and somatosensory brain regions during perception of trigeminal component. These findings suggest an association between frequent minty odor exposure and increased neurobehavioral sensitivity to intranasal trigeminal stimulation.

Appraisal and identification of different sources of smell by primary school children in the air quality test chamber of the SenseLab

ABSTRACT Previous studies have shown that next to ‘human smell’, ‘stuffy air’ is one of the discomforts that children report in classrooms. Besides, people’s olfactory system is able to recognize the perceived odour intensity of various materials relatively well and in many cases the nose seems to be a better perceiver of pollutants than some equipment. In the underlying study, the aim was to expose 335 primary children to different sources of smell, and ask them to evaluate and identify those sources at individual level with their noses. Additionally, the possible effect of plants on the reduction and/or production of smells was tested. Selected sources of odour were placed in different containers and the children were asked how they feel about the smell and to identify their source. The results showed statistically significant differences among children’s evaluations of different smells, a link between preference and recognition of odours, and, no statistical difference in the assessment of the smells when the potted plants were placed inside the CLIMPAQ. The results confirm the need to include sensory assessments in the evaluation of IAQ together with physical evaluations. Future studies on the effect of using active vegetation systems instead of passive systems are recommended.

Demand-controlled ventilation: do different user groups require different CO2-setpoints?

The aim of this study is to investigate whether children’s bioeffluent generation rate is proportional to their carbon dioxide (CO2) generation rate. Consequently, to assess if there is a need to differentiate the CO2- setpoint for different user groups, focusing on children. Perceived air quality (PAQ) and odour intensity (OI) were assessed in three classrooms in Oslo, Norway. Two second-grade classes (7-8 years old) were compared with one eighth-grade class (13-14 years old). An untrained test panel consisting of 16 people visited each classroom twice and were asked to evaluate PAQ and OI upon entering the classrooms. The CO2 levels in the classrooms were kept constant at either 600 ppm or 1100 ppm during each visitation. The results showed that average PAQ-score was significantly worse in the second-grade classrooms compared to the eighth-grade classroom. For perceived odour intensity, the average score indicated that the odour was stronger in the second-grade classrooms compared to the eighth-grade classroom, however, this difference in score was not significant. Our results indicate a need for differentiation of setpoints for CO2-DCV based on user groups, especially for children.