Marijuana is legal in Denver. It's pungent odor, however, is not.

More accurately, cloying scents of all sorts are prohibited by an old odor pollution ordinance in the Mile-High City. And now that Colorado has legalized the recreational use of marijuana, Denver's Department of Environmental Health has seen an influx of complaints from residents concerned about the drug's unmistakable smell.

Enter the Nasal Ranger, a "field olfactometer" that essentially works — and looks — just like a portable version of Futurama's fictional Smell-o-Scope. Except the Nasal Ranger is a real tool used for "measuring ambient odor dilution-to-threshhold," according to the Nasal Ranger's manufacturer, St. Croix Sensory.

(Fun fact: It also goes by the slang term "scentometer.")

Essentially, the Nasal Ranger measures the concentration of stinky particulate matter in the air to determine the strength of a given odor. California has used the tool to crack down on festering landfills, and St. Paul, Minn., employed it to quantify the lingering stench from stockyards.

How does it work? The History Channel's Modern Marvels, in an episode called "Stink," explains:

In Denver, there's a city ordinance that deems it an "unlawful nuisance for any person to cause or permit the emission of odorous air contaminants" that "interfere with the reasonable and comfortable use and enjoyment of property." A violation, which can carry up to a $2,000 fine, occurs when there is more than one volume of odorous air per seven volumes of odorless air.

Naturally, rodeos, stock shows, and "tarring operations" are exempt, per the ordinance. Marijuana is probably exempt, too — but for different reasons.

It would take an incredible amount of marijuana to broach that threshold, Ben Siller, a Denver DEH official, told the Denver Post. And there hasn't been a single odor violation in Denver in two decades.

Marijuana smoking or grow facilities won't reach that level, Siller said. Most grow facilities have ventilation systems and filters to prevent odors from escaping, even when marijuana cultivation is at its stinkiest during the harvest times, said Smith, owner of Higher Expectations. [Denver Post]

But with weed complaints rising, Denver is considering a marijuana-specific ordinance that would make public pot smoking and excessive smell-causing a crime.

Unless and until that passes though, parts of Denver will continue to smell like weed. And Jupiter will still smell like strawberries.