October  2002  No. 276

New Olfactometer, the Nasal Ranger

St. Croix Sensory, Inc. ( is a sensory evaluation and training facility located in Lake Elmo, MN. Since 1980 the company’s Odor Laboratory has specialized in odor testing of environmental air samples from industrial, municipal and governmental facilities. St. Croix Sensory has an experience base of work at over 250 municipal wastewater treatment plants, 150 industrial facilities, and 80 landfills and composting facilities. In recent years, St. Croix Sensory has focused on training odor monitors and inspectors; its training course is called “ODOR SCHOOL.®” A complement to St. Croix Sensory’s “ODOR SCHOOL” is the new Nasal Ranger Field Olfactometer that allows the user to quantify ambient odors.

St. Croix Sensory states that the Nasal Ranger is the state-of-the-art in field olfactometry for confidently measuring and quantifying odor strength in ambient air. It is portable and allows the user to determine ambient odor dilution-to-threshold (D/T) values objectively. The Nasal Ranger creates a calibrated series of discrete dilutions by mixing the odorous ambient air with carbon-filtered air. Field olfactometry defines each discrete dilution level as a D/T ratio. This ratio is a measure of the number of dilutions needed to make the odorous ambient air “non-detectable.”

The company maintains that field olfactometry with the Nasal Ranger is a cost-effective means to quantify odor strength. Applications include on site monitoring, random monitoring (i.e., random inspection), scheduled monitoring (data from a Nasal Ranger can be used to correlate the many parameters that influence odor episodes, including meteorological conditions and on site operating activities), intensive odor surveys (i.e., an in-depth evaluation of on site odor generation and off site odor impact to be used for permit renewal or facility expansion), citizen monitoring, complaint response and plume profiling, a protocol that supplements and “calibrates” air dispersion modeling.

Several features make the Nasal Ranger stand out as the state-of-the-art in field olfactometry, according to St. Croix Sensory. It has a specially-designed nasal mask, replaceable activated carbon cartridges, a selector dial, a controlled sniffing rate and traceable calibration. A check valve is placed in both the inhalation inlet and the exhalation outlet in order to control the direction of air flow while the olfactometer is being used. The activated carbon cartridges remove odors from the ambient air in order to render it “odor free” and used as the olfactometer dilution air. Orifices of different sizes allow the user to select the amount of dilution desired.

The Nasal Ranger is designed with a pressure sensor that monitors the static pressure through the olfactometer’s flow path. The user must sniff at a rate at which the static pressure is inside the target range. An LED alerts the user as to whether or not he/she is sniffing at the correct rate. The sniffing rate feedback loop standardizes the rate for all users of the olfactometer. The Nasal Ranger is factory calibrated to meet all specifications within the target range.

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