Almost four months into Colorado’s legalization of recreational marijuana for adults aged twenty-one and over, the weather is warming, windows are opening, and outdoor spaces are getting more use. All the while, a segment of the Colorado population, especially in the City and County of Denver (“Denver”), is exercising its new-found legal right to use marijuana. A pungent plant known for its skunk-like aroma, marijuana, accompanied by its distinct scent, is poised to waft onto properties across Colorado that may find the odor less than euphoric. The issue becomes whether these Denver residents have a legal avenue to control the once contraband odors from invading their living spaces, be it an adjacent apartment, backyard, or living room.
One option for Denver residents offended by marijuana’s musk is a nuisance suit. At the most basic level, nuisance claims are divided into public and private suits. While citizens are free to file a civil suit for private nuisance, a public nuisance is a public offense that requires state enforcement. See D.R.M.C. § 4-10 (describing a public nuisance under the air pollution control standards to be “unlawful”). Therefore, a citizen of Denver seeking to vaporize the smell of marijuana at his or her residence through a public nuisance suit will need to involve the Department of Environmental Health of the City. See id. (requiring the Department of Environmental Health of the City to investigate odor complaints).
Public Nuisance Suits:
Colorado Revised Statute section 31-15-401 affords the power to declare acts a public nuisance to municipalities under their police powers. C.R.S. § 31-15-401. Denver defines air pollution nuisances in two ways. D.R.M.C. § 4-10(b)(1)-(2). Denver considers it a per se nuisance if 1) “odorous contaminants are detected when one (1) volume of the odorous air has been diluted with seven (7) or more volumes of odor-free air” or 2) the Department of Environmental Health of the City “receives five (5) or more complaints from individuals representing separate households within the city within a 12-hour period relating to a single odor description, and the [Department of Environmental Health of the City] verifies the source of the odor.” Id.
An investigator with the Denver Department of Environmental Health has stated that neither marijuana smoking nor commercial grow facilities will reach the one-to-seven ratio for a per se violation. Jeremy P. Meyer, When Pot Smells in Denver, the Nasal Ranger Goes in to Investigate, The Denver Post (November 11, 2013). As for coordinated neighborhood complaints, Denver received 288 odor complaints, of which 16 related to marijuana, in all of 2012. Id. During the first nine months of 2013, Denver received only 85 objections to odors, of which 11 were marijuana related. Id. Part of this low complaint volume for marijuana odor is probably due to steps commercial grow facilities, including medical marijuana grow facilities, take to limit the odor emitted, such as the use of fans and carbon filters over exhaust vents. Id. Even if these odor controlling mechanisms malfunction, commercial grow facilities have an affirmative defense to any public nuisance citations related to odor as long as they take steps outlined in D.R.M.C. § 4-10(c) after realizing their in-house smell has gotten out. Additionally, smokers and growers alike may benefit from the holding in Hobbs v. Smith that “what is authorized by law cannot be a public nuisance.” Hobbs v. Smith, 493 P.2d 1352, 1354 (Colo. 1972).
The low level of public outcry regarding offensive marijuana odors and the remote possibility for marijuana growing or smoking to violate the required one-to-seven ratio make the likelihood of numerous public nuisance claims against growers or users of marijuana in Denver is slim. However, as 2014 is the first year for the expansion of legal use from medicinal-only to recreational as well, Denver officials will need to weather the summer months to determine if the public is truly alright with legalized cannabis consumption in Denver.
Despite the low likelihood that Denver officials will be reining-in marijuana use over the following months through nuisance suits, this does not change the fact that many residents have serious concerns about marijuana smoke making its way onto their private real property. Whether this is due to asthma, the presence of children, or a general distaste for the skunk-like smell, many people are concerned that recreational marijuana use might leave their backyards, front porches, or even living rooms unlivable due to a neighbor’s penchant for pot. This is where the private nuisance suit comes into play.
Private Nuisance Suits:
Colorado has long recognized that “regardless of compliance with zoning ordinances or regulations, both business and residential uses may be enjoined if they constitute a nuisance to an adjoining property owner or resident.” Hobbs, 493 P.2d at 1354. “To maintain a successful nuisance claim, a plaintiff must establish that the defendant has unreasonably interfered with the use and enjoyment of her property.” Pub. Serv. Co. of Colo. v. Van Wyk, 27 P.3d 377, 391 (Colo. 2001). “In making any determination of unreasonableness, the trier of fact must weigh the gravity of the harm and the utility of the conduct causing the harm. Generally, to be unreasonable an interference must be significant enough that a normal person in the community would find it offensive, annoying, or inconvenient.” Id. These fact-based standards for a nuisance suit create an issue ripe for a jury’s determination. See Miller v. Carnation Co., 516 P.2d 661, 664 (Colo. App. 1973) (overturning trial court’s acts of discharging the jury and dismissing the plaintiff’s nuisance claim at the conclusion of trial, but upholding trial court’s determination that the plaintiff was not entitled to injunctive relief). Such fact-dependent issues make the ability for a defendant to succeed in a Motion to Dismiss or Motion for Summary Judgment less likely.
However, a plaintiff’s ability to prove that legal growing or smoking is ultimately unreasonable is still unlikely. Colorado has some published judicial opinions about odors causing a nuisance. See generally Hobbs, 493 P.2d 1352; and Miller, 516 P.2d 661. However, these opinions do not address nuisance claims based solely on odor, but instead refer to the maintenance of an industrial chicken farm in Miller, where the owner’s refusal to adequately clean-up chicken excrement created a breeding ground for flies that caused damage to the neighbor’s house and conditions that rendered being outside rather unbearable, and the boarding of horses in a residential neighborhood in Hobbs, where, again, manure maintenance was less than stellar and resulted in flies and odors. See Hobbs, 493 P.2d at 1353–54; Miller, 516 P.2d at 662–63. While the Hobbs plaintiff did succeed in enjoining her neighbor from boarding a horse (Hobbs, 493 P.2d at 1355), the plaintiff in Miller lost as a matter of law regarding his claim for injunctive relief against the commercial chicken farm’s manure and fly onslaught. Miller, 516 P.2d at 665. Successful plaintiffs in Allison v. Smith showed that, beyond odor, the neighbors filled their property with:
“inoperable automobiles, large rigs, a bulldozer, tons of scrap metal, pipe, new and used construction materials, drums of petrochemicals, large amounts of everday litter and rubbish, and other ‘obnoxious debris’ . . . installed several above ground 2,000-gallon oil and fuel storage tanks directly uphill from the [plaintiffs’] cabin. . . . poured oil on the ground to ‘keep the dust down’ . . . [which was] carried by rain and snow melt from the [defendants’] land onto the [plaintiffs’] property, killed much vegetation on their land, entered their water well, making the water unusable . . . ”
Allison v. Smith, 695 P.2d 791, 793 (Colo. App. 1984). All of this was in addition to “creat[ing] a persistent odor.” Id.
Comparing the facts from these previous nuisance cases to a neighbor with six marijuana plants in a closet or a blunt on the back porch every two hours, it is hard to see success. This is especially true because of the balancing test that requires “weigh[ing] the gravity of the harm and the utility of the conduct causing the harm.” Pub. Serv. Co. of Colo., 27 P.3d at 391. While smoking marijuana has little, if any, social utility, a plaintiff is hard-pressed to show the harm caused, absent an asthma condition or some other health problem, that a neighbor’s marijuana consumption may aggravate. Therefore, absent a serious health concern, plaintiffs may struggle to marshal facts that will result in a successful private nuisance claim against marijuana odors. This leaves negotiation of marijuana use on private residential property and its effects on neighbors to be dealt with between neighbors, rather than through the legal process. The next question becomes: can the local conflict resolution boards handle the possible torrent of tiffs between warring neighbors? Only time will tell.
 While Colorado passed Amendment 64 to its Constitution, effective January 1, 2014, legalizing recreational marijuana, Colorado has had legal medicinal marijuana since 2000, when citizens passed Section 14 of article XVIII of the Colorado Constitution. While medical marijuana presented the same problems, passage of Amendment 64 could significantly increase the amount of marijuana used in Colorado, making the issues addressed in this article more likely to occur.
 The general definition of a nuisance under the D.R.M.C. governing air pollution control also contains a catch-all provision that mirrors the private nuisance claim detailed in the following section.
 In contrast to the lack of complaints against marijuana grow facilities, a wood-burning pizza restaurant in a Denver neighborhood received successive complaints and a citation from Denver, resulting in the installation of a system to diffuse the smoke it produced. Jeremy P. Meyer, When Pot Smells in Denver, the Nasal Ranger Goes in to Investigate, The Denver Post (November 11, 2013).
 It is also important to note that Denver has a separate municipal ordinance regarding smoking or displaying marijuana in public that makes it “unlawful for any person to openly and publicly display or consume one (1) ounce or less of marijuana.” D.R.M.C. § 38-175(b). However, the same ordinance allows for the consumption of marijuana on “private residential property” when the person consuming is “an owner of the property, a person with a leasehold interest in the property, or has been granted express or implied permission to consume marijuana on the property by the owner or lessee.” D.R.M.C. § 38-175(d). This exception makes municipal enforcement of marijuana use that offends Denver citizens in their own homes unlikely to be effective in terms of protecting real property residents who find such use or smell offensive, as neighbors smoking on their own property is allowed.