Odor

Physiology of smell and smell acuity

• Odor perception is mediated by the olfactory nerve.
• Olfactory receptor cells are neurons found in the olfactory epithelium.
• Odorous molecules bind to receptor proteins on cilia, initiating electric signals.
• Signals travel along olfactory nerves to the olfactory bulb in the brain.
• Olfactory information is processed in the olfactory cortex and forwarded to the central nervous system.
• Ability to identify odor varies among individuals and decreases with age.
• Women generally outperform men in odor discrimination, but studies show conflicting results.
• Pregnant women often have increased smell sensitivity.
• Sense of taste decreases with age as smell dominates.
• Chronic smell problems increase with age, particularly after 70 years old.

Smell acuity compared to other animals

• Humans have a good sense of smell despite having fewer olfactory receptor genes than mice.
• Smell can induce pleasure, warn of danger, locate mates, find food, and detect predators.
• Humans can distinguish approximately one trillion unique aromas.
• Flavorists and perfumers can identify discrete chemicals in complex mixtures using only smell.
• There has been an apparent evolutionary decline in the human sense of smell.

Habituation or adaptation

• Familiar odors, like body odor, are less noticeable due to habituation.
• Continuous odor exposure leads to fatigue, but the sense of smell recovers with stimulus removal.
• Odors can change depending on environmental conditions, such as cool dry air.
• Habituation affects the ability to distinguish odors and focuses on differences and changes.
• Mixing odorants can block the perception of habitual odorants and adjust sensitivity to differences.

Genetic component

• Thousands of olfactory receptor gene sequences are known.
• Olfactory receptors are seven-helix-turn transmembrane proteins.
• There is a conserved sequence in most olfactory receptors that serves as a metal-ion binding site.
• Copper is essential for the detection of certain odorants.
• The specific metal ion binding site in olfactory receptors is still under study.

Measuring techniques, concentration, perception, sampling, regulation, and control

• Sensory evaluation: Using human senses to detect and evaluate odor presence.
• Chemical analysis: Identifying and quantifying specific odor-causing compounds.
• Electronic noses: Instruments that mimic the human olfactory system to detect and analyze odors.
• Dynamic olfactometry: Measuring odor concentration by diluting the sample and determining the dilution ratio.
• Gas chromatography: Separating and analyzing odor compounds based on their chemical properties.
• Odor concentration refers to the pervasiveness of an odor.
• It can be measured using techniques like dilution and dynamic olfactometry.
• The concentration of odor-causing compounds determines the intensity of the odor.
• Different odor thresholds exist for various compounds, indicating the minimum concentration required for detection.
• High odor concentration can lead to annoyance, discomfort, and health issues.
• Odor perception varies among individuals due to genetic and environmental factors.
• The human nose can detect a wide range of odors, from pleasant to unpleasant.
• Odor perception can be influenced by factors like age, gender, and cultural background.
• The brain processes odor information in the olfactory cortex, contributing to the perception of smell.
• Perception of odor can trigger emotional and memory responses in individuals.
• Proper sampling techniques are crucial for accurate odor measurement.
• Sampling methods include grab sampling, passive sampling, and active sampling.
• Sample collection should consider factors like temperature, humidity, and airflow.
• Sampling locations should be representative of the odor source and its surrounding environment.
• Sampling frequency and duration depend on the variability and persistence of the odor.
• Odor regulations exist in many industries to minimize the impact of odors on the community.
• Regulatory agencies set odor standards and guidelines for different sectors.
• Odor control measures include source reduction, containment, and treatment.
• Technologies like biofilters, activated carbon filters, and chemical scrubbers are used for odor control.
• Continuous monitoring and periodic assessment help ensure compliance with odor regulations.

Odor Data Sources

Reference	URL
Glossary	https://www.alternix.com/blogs/glossary-of-terms/odor
Wikipedia	http://en.wikipedia.org/wiki/Odor
Wikidata	https://www.wikidata.org/wiki/Q485537
Knowledge Graph	https://www.google.com/search?kgmid=/m/01jqkv