Wikipedia:Nasal Ranger

The Nasal Ranger is a device made by St. Croix Sensory that uses the science of olfactometry to measure the strength of smells. The generic name for this type of device is field olfactometer.

Design and applications
The Nasal Ranger works via dilution. The device has a filtration system that can produce nearly pure air. During operation, the user breathes this filtered air for at least one minute in order to cleanse their 'nasal palate'. The user then turns a dial which allows in a tiny amount of ambient air alongside the filtered air. Next, the user inhales twice and turns the dial to the next step, this one delivering solely filtered air, to cleanse the palate again. Each subsequent step increases the amount of unfiltered ambient air taken in, and is always followed by a cleansing of the palate. The step on the dial where the user first smells the problem odor determines the dilution-to-threshold ratio (D/T). Strong smells have a high D/T. In its standard configuration, the highest D/T the Nasal Ranger can measure is 60 (60 parts filtered air to 1 part ambient air). A D/T this high would be associated with a very strong odor. In cases where an odor with a D/T stronger than 60 must be measured, the Nasal Ranger can be configured to quantify a higher D/T. Strong odors only require the introduction of a tiny amount of ambient air to be detected. A D/T of 2 would be associated with a weak smell.

ODOR TRACKR, a web-based application, is available for use with the Nasal Ranger. ODOR TRACKR is a data logging tool which stores D/T values for each sample taken, as well as other information such as odor characters, sample time, date, and geographical position determined via the Global Positioning System.

The Nasal Ranger was introduced in 2000. Designed by St. Croix Sensory, the Nasal Ranger was created to help determine the seriousness and validity of complaints of bad smells from animal farms, sewage plants, landfills,  compost piles, factories, and other industrial and agricultural activities likely to generate strong odors. Many local governments have used the instrument to help regulate Cannabis use and production.

Operators of the Nasal Ranger must be screened for olfactory capability before use. The manufacturer offers an "Odor School" to train operators on proper use of the Nasal Ranger.

With training and additional accessories, a Nasal Ranger package costs approximately $3,400.

Users
Many state and local governments use the Nasal Ranger. The Denver, Colorado municipal Department of Environmental Health has purchased several Nasal Rangers to help determine if the smell of cannabis or other substances at any given location is strong enough to merit a fine or other regulatory action. Denver treats any smell, with exemptions for rodeos, stockyards, and tarring operations, with a D/T above 7 as a violation. A Denver official said it is rare to find smells so strong as to exceed this standard. California uses the Nasal Ranger to help regulate landfills. South Saint Paul, Minnesota uses Nasal Rangers to regulate the odor of its stockyards. Yolo County, California and Las Vegas, Nevada are also known to use the device.

In popular culture
The Nasal Ranger was featured on an episode of The History Channel's program Modern Marvels called "Stink."

Many commentators in the media have noted that the Nasal Ranger strongly resembles the "Smell-O-Scope" created by Professor Farnsworth, a character in the animated comedy Futurama.