Entomologist Donald Barnard demonstrates the attraction of female yellow fever mosquitoes to his hand in an olfactometer

An olfactometer is an instrument used to detect and measure

odor An odor (American English) or odour (Commonwealth English; see spelling differences) is caused by one or more volatilized chemical compounds that are generally found in low concentrations that humans and animals can perceive via their sense ...

dilution. Olfactometers are used in conjunction with human subjects in laboratory settings, most often in

market research Market research is an organized effort to gather information about target markets and customers: know about them, starting with who they are. It is an important component of business strategy and a major factor in maintaining competitiveness. Ma ...

, to quantify and qualify human

olfaction The sense of smell, or olfaction, is the special sense through which smells (or odors) are perceived. The sense of smell has many functions, including detecting desirable foods, hazards, and pheromones, and plays a role in taste. In humans, ...

. Olfactometers are used to gauge the odor detection threshold of substances. To measure intensity, olfactometers introduce an odorous gas as a baseline against which other odors are compared. Many scientists use the term "olfactometer" to refer to a device used to study insect behavior in presence of an olfactory stimulus. It consists of a tube with a bifurcation (with "T" or "Y" shape) where an insect walks and decides between two choices, usually clean air versus air carrying an odor. This is why this device is also called dual choice olfactometer. Alternatively, an olfactometer is a device used for producing aromas in a precise and controlled manner.

Flow-olfactometer

Description

A flow-olfactometer is a difficult instrument for creation of well defined, reproducible odor or pain stimuli in the nostril without tactile or thermal stimulation. Stimulus rise time is fast enough to allow for recording of olfactory

evoked potential An evoked potential or evoked response is an electrical potential in a specific pattern recorded from a specific part of the nervous system, especially the brain, of a human or other animals following presentation of a stimulus such as a light f ...

s (OEPs).

How a flow-olfactometer works

A flow-olfactometer produces a constant heated and humidified flow of pure air. This air flow runs continuously to the subjects nose. For the length of the stimulus pulse the continuous air flow is replaced by a bloc of odorized air.

Dynamic dilution olfactometer

The new generations of dynamic dilution olfactometers quantify odors using a panel and can allow different complementary techniques: odor concentration and odor threshold determination, odor suprathreshold determination with comparison to a reference gas, hedonic scale assessment to determine the degree of appreciation, evaluation of the relative intensity of odors, and allow training and automatic evaluation of expert panels. The most recognised olfactometry standard is currently the EN13725 standard. Analyses performed by olfactometers are often used in site diagnostics (multiple odor sources) performed with the goal of establishing odor management plans.

Field Olfactometry

Field olfactometry can be a useful tool in validating odor complaints, or determining odor levels for various locations. Field olfactometers provide the same basic function of a laboratory olfactometer but are designed to be used by a single panelist to measure ambient odors. To be classified as a field olfactometer the device must be able to provide accurate and controlled dilution of the ambient air with odorless air and present the diluted sample to the panelist at controlled and positive air flow. The Nasal Ranger, developed by St. Croix Sensory, is a common brand of field olfactometer used in wastewater treatment plants, industrial facilities, and marijuana grow houses.

Verifying Odorant level in Natural Gas

Natural gas odorant concentrations are required to be readily detectable at one-fifth of the lower flammable limit of the gas by state and federal regulation. Many gas companies utilize olfactometers to verify this standard. The

ASTM ASTM International, formerly known as American Society for Testing and Materials, is an international standards organization that develops and publishes voluntary consensus technical standards for a wide range of materials, products, systems, an ...

has published a standard test method for this determination.

References

CEN 13725:2003 - Air quality - Determination of odour concentration by dynamic olfactometry; German version EN 13725:2003. {{Olfactory receptors Olfaction Neurophysiology Sensors