Since Colorado voters legalized marijuana last November, reports of pot odor are no longer subject to criminal investigations. In Denver, the city’s Department of Environmental Health handles such complaints, examining cultivation sites and determining whether or not a given odor constitutes a fineable violation. Last year a grand total of 16 odor complaints were filed with the city (up from seven in 2010).

In order to investigate those complaints, the department has embraced the Nasal Ranger. The Nasal Ranger is a patented device that augments the human sense of smell to ascertain if a given pot grow odor is beyond the acceptable legal parameters. The Ranger is a portable odor-measuring device (resembling a radar gun or a megaphone). A nasal mask is placed over the user's nose enabling him or her to detect the intensity of odor by filtering out odorous air.  

Such field olfactometers allow Environmental Health investigators to measure whether or not an odor reaches a ratio of 8:1 or higher. If so, it violates the city's odor ordinance and could result in a fine of up to $2,000. 

Mike McGinley, Laboratory Director at St. Croix Sensory Inc (the manufacturers of the Nasal Ranger), explained how the device works:  

“The Nasal Ranger is a dilution device. You increment different dilution ratios to determine what dilution amount you begin to smell the odor. An inspector normally starts at high dilution and does not smell anything through the Nasal Ranger. They continue to increment to less and less dilution until they just start to smell the odor. In Colorado, if you detect an odor at an eight or higher (eight or more dilutions), then the facility would be in violation of the state odor rule. Actually, it is a bit more complex as they must record eight or higher two times in an hour with at least 15 minutes between the readings. The 8:1 means eight parts of dilution air to one part of odorous air, or it means the air you are standing in diluted 8 times." 

In reporting this story, 7News accompanied an Environmental Health investigator to follow up on a complaint at a grow site, but the Nasal Ranger didn't pick up any pot odors strong enough for a citation to be issued. 

However, a Nasal Ranger reading isn't Environmental Health's only standard – if five households complain about a given grow site's odor within a 12-hour period, that also constitutes a violation. 

Expect a spike in odor complaints and more utilization of the Nasal Ranger once retail pot sales in Denver begin in 2014 – even though the city has released a guide establishing acceptable management practices for commercial pot production, including the best methods of ventilation and odor control.