As automobiles, houses, oil refineries, a copper smelter, a medical-waste incinerator and other machines of society belched out pollution along the Wasatch Front last week, much of this waste rose to a certain height in the atmosphere and then got trapped near the Salt Lake Valley floor, like a moth in a Mason jar.

This marvel of nature and science—the inversion, an annual collision of geography, weather and modern-day humanity—comes with many consequences. Elderly folks and those with respiratory issues are stressed; children can't play outdoors during school recess, and neighbors rat out neighbors when they spot smoke billowing from a chimney.

But the inversion is also a catalyst for activism. Clean-air advocates say that as winter sets in, and as the brown sludgy air begins to harden in Utahns' lungs, their phones start ringing and complaints roll in. A general heightened awareness surrounding air-quality issues takes hold.

"It's interesting as an air-quality organizer, because for us to rally around [improving air quality], we know that we need bad air," says Carl Ingwell, founder of the organization CleanAirNow! "We know that people need to see it, and we know that people need to feel the effects."

As a high-pressure weather system settled over Utah in early December, the factors that create an inversion roared back into focus. In simple terms, inversions occur when high-pressure weather systems trap pollutants inside Salt Lake's bowl-shaped valley with its surrounding mountains. The foul air sticks around until a less stable system—think storms—passes through.

On Dec. 4, an air-quality monitoring station at Hawthorne Elementary School in Salt Lake City measured particulate pollutants at 45 micrograms per cubic meter, a level deemed by the Utah Department of Environmental Quality as "unhealthy for sensitive groups." While residents across northern Utah cursed the filthy air, groups that advocate for cleaner air also began to ramp up for their busiest time of the year.

Matt Pacenza, executive director of HEAL Utah, says that even though individuals who drive to work and heat their homes play a role in creating air pollution and, even though changing individual behaviors can make an impact, regulations born at the Legislature are also important.

As the 2016 legislative session approaches, Pacenza says two efforts are afoot to help make homes cleaner. One would require new water heaters sold in the state to limit emissions of nitrogen oxide, a major contributor to dirty winter air. Although this proposal received a favorable nod in September from the Utah Air Quality Board, it hit a wall in October when lawmakers on the Administrative Rules Review Committee fielded concerns raised by the Utah Home Builders Association, and the rule was put on the back burner.

Pacenza also hopes to see a bill that would bring Utah's building codes up to 2015 standards. Clean-air advocates say the last serious revamp of building codes came in 2006, and that state law allows the codes to be updated every three years, in step with national regulations.

But during the 2015 session, the state came close to moving even farther away from more efficient construction standards. A bill that could resurface this year, sponsored by Rep. Brad Wilson, R-Kaysville, a developer, proposed to defer building-code updates to every six years, which could prevent Utah from making an update until 2021.

Requiring the sale of efficient water heaters and keeping building codes up to date are two of the easiest things Utah can do to improve air quality, Pacenza says. "They're just two really good things that should have kind of sailed through interim committees to be passed this spring, and, instead of sailing through, they're both hitting these hurdles," Pacenza says.

When it comes to the Legislature, it's difficult to gauge how interested the stout Republican majority—many of whose members reside outside the Wasatch Front—is in making it easier to breathe in the state's most populated areas.

The winter of 2013-14 saw some of the worst inversions in recent state history, with 49 "action" days, where particulate matter hovered at or above 15 micrograms. And the bad days outnumbered the "kinda" bad days, with 31 of these action days seeing particulate matter at 25 micrograms or higher.

But that filthy air year turned out to be one of the most fruitful at the Legislature, at least for clean-air advocates. According to HEAL's statistics, nine bills aimed at improving air quality were passed, and $4 million was allocated for clean-air programs.

The 2013-14 winter also saw what might have been the largest environmental rally in state history when more than 4,000 people showed up on the south steps of the Capitol to protest the state's poor air quality.

In 2014-15, though, with balmy temperatures allowing pollution to drift away and only 36 "action" days recorded by state regulators, the Legislature approved only four air-quality bills, and far fewer citizens turned up on the Capitol steps to rally for clean air.

It's difficult to know if fewer dirty-air days took the burden off of lawmakers to make clean air a priority, but Ingwell believes the two could be connected. "We had an off year last year," he says. "We didn't see much political activity last year. As bad as it sounds, I hope this year is a little different; we're brought back to reality, and people make serious investments in the issue, and we can see some serious strides forward."

Of course, the Legislature can do only so much. According to the Utah Department of Air Quality, mobile sources of pollution, such as cars, trains and airplanes, are responsible for spewing 57 percent of the chemicals that end up resulting in poor air quality. The heating of homes and small stationary sites accounts for 32 percent, while industrial sources, like the valley's oil refineries, copper mine and the notorious medical-waste incinerator in Bountiful, account for a mere 11 percent.

These statistics, Ingwell says, place the burden of cleaning up the air somewhat unfairly on the shoulders of, well, everyone. And this is where improving Utah's air quality gets complicated. For drivers to flee the interior of their automobiles, public transportation must become more accessible, Ingwell says. And for public transportation to become more accessible, lawmakers must invest in expanding public transportation and communities that are planned around moving people without burning fuel.

"That's easy for state government to say, and then, kind of sidestep the problem and say, 'Our hands are clean, the public needs to drive less,'" Ingwell says. "Any policy that puts the onus on us should be backed up by government policies that help allow for that."

But individuals can make a difference—even at the Capitol. Roughly three years ago, Ingwell says, everyone he knew was angry about the air. "I thought, 'Why can't we channel all this anger into something productive?'" he says. "I stepped up and took the lead on that and wanted to be someone that helps my friends and my community members to speak up and voice their concerns."

While Pacenza's HEAL Utah and Ingwell's CleanAirNow! advocate inside the granite walls of the Capitol for cleaner air, Brian Moench, president of Physicians for a Healthy Environment, says it's important for individuals to take steps to clean the air. And when the inversion is in place—when all residents need to do is take a breath and look to the horizons to see tiny bits of their own dirtywork—Moench says Utahns should take stock in what they can do to live cleaner lives.

With air that you can see and taste, Moench says, it's vivid to ask, "What would the air look like if everybody did what I did?"

"The public's engagement and concern is obviously ramped up significantly during inversion season," Moench says. "Unfortunately, we're sometimes in the awkward position of rooting for bad air, just so we can maintain some engagement on the issue."