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Deep Sky is running a carbon removal competition on the plains of Alberta.

Four years ago, Congress hatched an ambitious, bipartisan plan for the United States to become the epicenter of a new climate change-fighting industry. Like an idea ripped from science fiction, the government committed $3.5 billion to develop hulking steel complexes equipped with industrial fans that would filter planet-warming carbon dioxide out of the air.
That vision — to build regional hubs for “direct air capture” — is now languishing under the Trump administration. But a similar, albeit privately-funded initiative in Canada has raced ahead. In the span of about 12 months, a startup called Deep Sky transformed a vacant five-acre lot in Central Alberta into an operational testing ground for five different prototypes of the technology, with more on the way.
I had been following the project since early last year, after receiving roughly a dozen press releases from Deep Sky about all of the companies it was setting up partnerships with. But it was hard to believe the scope of the ambition until I saw it with my own eyes.
CarbonCapture Inc., one of the companies piloting its technology at Deep Sky, had originally planned to deploy in the U.S., but has since packed up and headed north. The Los Angeles-based startup recently shipped all the equipment for its first demonstration project from Arizona to the Deep Sky site on four flatbed trucks. On a crisp October day, under a bluebird sky, the company’s CEO Adrian Corless stood in front of the newly installed towering mass of metal fans and explained the move.
“Because of what’s been going on in the U.S. and the backing away from support of climate technology and carbon removal, we made a decision back in February that we were going to redirect our focus and effort to Canada,” he told an audience of Canadian officials who had come to see the tech up close.
“Eight weeks ago, this was just dirt,” Corless said. “Today, we’re actually going to bring the first of our modules to life.” Then he invited Danielle Smith, Alberta’s conservative Premier, to do the honors. She pointed her fingers like a pistol and yelled, “Hit it!”
Behind her, the fans started to whir.
Deep Sky is not like other companies working in direct air capture, or DAC. Whereas most startups are developing their own patented designs and then raising money to go out and build demonstrations, Deep Sky is solely a project developer. It buys DAC systems, operates them, and sells credits based on the amount of carbon it’s able to remove from the air and sequester underground. Other companies buy these credits to offset their own emissions.
In the spring of 2024, Damien Steel, Deep Sky’s then-CEO, explained the theory of the case to me. It takes a different set of skills to engineer the tech than to deploy it in the real world, he said, which requires procuring energy to run the system and developing storage sites for the captured CO2. “There’s a reason why renewable developers don’t build their own windmills and solar panels,” he told me.
DAC technology is nowhere near as advanced as solar panels or wind turbines. Removing carbon dioxide from the air, where it makes up just 0.04% of the total volume, is currently far too energy-intensive to be commercially viable. There are more than 100 companies around the world trying to crack it.
Deep Sky’s first ambition was to buy a bunch of prototypes, test them next to each other, and figure out which were the most promising. Steel told me he was in the process of acquiring 10 unique DAC systems to install at a “commercialization and innovation center” known as Deep Sky Labs.

By the end of that summer, the company had signed a lease for the site in Alberta. Less than a year later, this past June, it had completed initial construction and was ready to begin hooking up DAC systems. In August, it announced that it had successfully injected its first captured carbon into an underground storage well. I had never seen one DAC project in the real world, let alone five. The company suggested I come for a tour during CarbonCapture’s launch event in late October.
By then Steel, who joined Deep Sky after more than a decade in venture capital, had stepped down from the CEO role “for personal reasons,” he wrote in a LinkedIn post, though he stayed on as an advisor. My guide would be his successor, former Chief Operating Officer Alex Petre.
Deep Sky Labs, now called Deep Sky Alpha, is in Innisfail, a town of about 8,000 people surrounded by farmland and prairie. To get there, I flew to Calgary and drove 75 miles north on Highway 2, the primary throughway that connects to Edmonton. Innisfail is dense and suburban-looking, with an industrial corridor on the western edge of town. Deep Sky was on its outermost edge, on the site of a former sewage lagoon the town had recently reclaimed, and sat catty corner to a welding and manufacturing company, which, as I was later told — multiple times — was developing hydrogen-powered locomotives.
A bright white cylindrical building about the size of an airplane hangar, emblazoned with “Deep Sky” in big black letters, was visible from half a mile away. As I pulled up to the site, workers in neon vests and hard hats were scurrying among outcroppings of pipes and metal structures. Unsure of where to enter, I parked on the road and wandered up to some trailers outside the perimeter. Petre poked her head out of one and beckoned me inside an office, where she fitted me with my own vest and hard hat so I could get a closer look.
“This is the only place in the world where we are putting together different direct air capture technologies side by side,” she told me, as we passed through a gate and began walking the grounds. Other than the sound of trucks and excavators driving around, it was fairly quiet. None of the DAC units were operating that day — one was down for maintenance, one for the winter, and the rest were still under construction.
The first stop on the tour was a modest black shipping container labeled SkyRenu, a DAC company based in Quebec. It was the smallest system there, designed to capture just 50 tons of carbon per year — roughly the annual emissions from a dozen cars. Directly across from it, workers appeared to be fitting some pipe on a much larger and more complicated structure resembling Paris’ Pompidou Center. This was United Kingdom-based AirHive’s system, which would have the capacity to capture about 1,000 tons per year once completed.

DAC systems are feats of chemistry and mechanical engineering. At their core is a special material called a sorbent, a liquid or solid designed to attract carbon dioxide molecules like a magnet. The process is generally as follows:. First, the sorbent is exposed to the air, often with the help of fans. Once saturated with carbon, the sorbent is heated or zapped with electricity to pry loose the CO2. The resulting pure CO2 gas then gets piped to a processing facility, where it’s prepared for its ultimate destination, whether that’s a product like cement or fuel or, in the case of Deep Sky, a deep underground rock formation where it will be stored permanently.
Deep Sky’s aim was to trial as many iterations of the tech as it could at Alpha, Petre told me. That’s because what works best in Alberta’s climate won’t necessarily be optimal in Quebec or British Columbia, let alone hotter, more humid zones. “When the feedstock, which is ambient air, ends up being so different, we need multiple different technologies to work,” she said.
Case in point: A DAC system designed by Mission Zero, another U.K company, was offline the day I visited — and would remain so until next spring. It utilized a liquid sorbent and had to be drained so that the sorbent wouldn’t freeze when temperatures dropped below freezing overnight. The challenge wasn’t entirely unique to Mission Zero, however. “Everyone is struggling with winter,” Petre told me.

Alpha is piloting systems with liquid sorbents and solid sorbents, variations on the chemistry within each of those, and systems that use different processes to release the carbon after the fact. The development cost ran to “over $50 million” Canadian, Petre told me. The company raised about that amount in a Series A back in 2023. It also won a $40 million grant from Bill Gates’ venture capital firm Breakthrough Energy in December 2024, and this past June, the Province of Alberta awarded Deep Sky an additional $5 million from an emissions-reduction fund paid for by fees on the fossil fuel industry.
The company fully owns and operates almost all of the DAC units onsite, although it’s still working with the vendors to troubleshoot issues and sharing data with them to improve performance.
When it comes to Carbon Capture Inc., however, the arrangement is a bit different. Deep Sky has agreed to host the company’s tech, giving it access to power, water, and underground CO2 storage, but CarbonCapture will retain ownership and help with operations, and the two companies will share the proceeds from any revenue the unit generates.
Petre said the structure was mutually beneficial — Deep Sky gets to demonstrate its strengths as a full-service site developer, while CarbonCapture gets access to a plug-and-play spot to pilot its system in the real world. The U.S. company is also looking to expand in Canada. “There’s lots of potential collaboration down the line,” Petre said.
Before Trump arrived at the White House, CarbonCapture had been making aggressive plans to grow in the states. In the fall of 2022, before the company had even demonstrated its tech outside of a lab, it announced that it would build a project capable of removing 5 million tons of carbon per year in Wyoming by 2030. It later leased an 83,000-square-foot manufacturing facility in Arizona to produce the equipment for the project.
At the time, the Biden administration was integrating carbon removal — of which DAC is just one variety — into its “whole-of-governement” climate strategy. The Department of Energy rebranded its Office of Fossil Energy to reflect a new focus on “carbon management,” a broad term that encompasses carbon captured at fossil fuel plants as well as from the atmosphere. In addition to overseeing the development of the DAC Hubs, the agency was running more than a dozen other grant programs and research initiatives mandated by Congress that were intended to help the nascent industry get established in the U.S. Biden’s 2022 climate law, the Inflation Reduction Act, also increased the tax credit available to DAC projects from $50 for every ton of carbon stored underground to $180.
As helpful as all of that may have been for the nascent industry, Canada was arguably going further. In 2022, the country finalized its own tax credit — an investment tax credit — that would cover 60% of the capital cost of building a direct air capture plant. The approach, while inspired by the U.S. subsidy, is geared more at de-risking project development than rewarding project success. The following year, the province of Alberta said it would offer an additional 12% investment tax credit on top of that.
Alberta was also becoming a leader in developing carbon storage infrastructure. Despite — or, more likely, because of — its oil-based economy, the province views carbon capture and storage as a “necessary pathway” that “will help Alberta transition to a low-carbon future.” Canada is the fourth largest producer of crude oil in the world, and the bulk of it comes from Alberta’s environmentally destructive tar sands.

The government of Alberta owns most of the subsurface rights there, unlike in the U.S., where such rights are bestowed to landowners. That meant the province could simply offer companies leases to develop carbon injection wells. After two requests for proposals, the province selected 24 projects to “begin exploring how to safely develop carbon storage hubs.” A few of them, including Deep Sky’s storage partner — the Meadowbrook Hub Project north of Edmonton — are now operating.
Corless, of CarbonCapture, told me he spent a lot of time in Washington talking to the new staff at the DOE after Trump’s inauguration. It became increasingly clear to him that the DAC Hubs funding — and the general support for the sector enjoyed under the previous administration — would be going away.
By that point, the company had already planned to move its Wyoming venture to Louisiana after struggling to secure a grid connection at its original site. CarbonCapture had been awarded a DAC Hubs grant to conduct an engineering study for the project, but it received a notice from the DOE that the grant was canceled earlier this month. The company is still considering its options for how or whether to move forward.
On the same day the news leaked, CarbonCapture announced that it was shifting its plans to build a separate, 2,000 ton-per-year pilot plant from Arizona to Canada. Corless told me the company had originally planned to partner with a cement company to store the captured carbon in building materials, but Alberta offered more attractive commercial prospects. The company could more quickly access geologic carbon storage there, enabling it to sell carbon credits, which command a higher price than experiments in carbon-cured cement.
The timing of the announcement was pure coincidence. The poor prospects for an American DAC industry under Trump weren’t not a factor in the move, however. CarbonCapture wanted its pilot project to be a “springboard” for its first commercial plant, and Canada was attractive “given the favorable economic incentives, favorable regulatory environment, and the general positive interest in deploying DAC,” the company’s marketing director, Ethan Stackpole, told me in an email. “This is in contrast to the current atmosphere in the U.S.”
CarbonCapture signed a contract with DeepSky to host the pilot, dubbed Project Tamarack, in May, and set up a Canadian business entity called True North to build it. When I visited the site, the company was in the final stages of “commissioning” the unit, i.e. getting it ready to operate. The equipment had been manufactured at the company’s factory in Arizona, but it may end up being the only system produced there. The facility is now sitting idle.
Petre and I followed the tidy rows of wires and pipes that wound through Deep Sky Alpha, carrying electricity, water, and compressed air to each DAC system. A set of return pipes delivers the captured CO2 to Deep Sky’s central processing facility — the big white cylindrical building — where the company measures the output from each system before combining it all into a single stream. Inside, she showed me how the gas moved between large, tubular instruments that measure, dry, compress, and cool it into a liquid.
“Everything outside is first of a kind,” she said. “All of this equipment in here is fairly standard energy oil and gas equipment, it’s just arranged in a very different way.”
Sensors monitoring the wires and pipes enable Deep Sky to measure how much energy and water goes into producing a ton of CO2. Finally, trucks carry away the liquid CO2 to the Meadowbrook storage hub about two hours north, where an underground carbon sequestration well operated by a separate company called Bison Low Carbon Ventures provides it a permanent home.
While trucking the CO2 wasn’t ideal, the amount Deep Sky would capture at Alpha was so small that it made more sense to partner with Bison, which already had a permitted well, than to try to build one itself, Petre explained. When Deep Sky scales up at its next facility, which it expects to build in Manitoba, the company aspires to drill its own carbon sequestration wells on site.
Despite Alberta’s advantages for DAC, the location is not without drawbacks. The province had imposed a seven-month moratorium on renewable energy approvals from 2023 to 2024, which led to project cancellations and put development on ice. When the ban lifted, new regulations restricting wind and solar on agricultural land and near designated “pristine viewscapes” continued to make it difficult to build. Petre told me Deep Sky was one of only two companies in Alberta to secure a power purchase agreement with a solar farm last year.
“If I said, ‘I need 150 megawatts for my next facility right now,’ it would be a fairly difficult process,” she said. “There isn’t that much capacity online, and I would have to compete with data centers and a whole bunch of other folks who are also looking to come here and develop.” The company has started looking into building its own renewable energy supply on site, she said.
That anti-renewable sentiment stems from the region’s strong oil and gas identity. After my tour with Petre, I sat through a short program celebrating Project Tamarack’s launch, where Alberta’s Premier Danielle Smith conveyed her excitement by asserting that the province was “working to phase out emissions, not oil and gas production.” Alberta would double its energy production in the coming years, she said, while still reaching a goal of carbon neutrality by 2050.
Of all the extraordinary things I had seen and heard that day, this was the most brazen. The promise of direct air capture — the entire reason to expend time and energy and funds on plucking CO2 molecules out of the air — is that it’s one of the few ways to clean up the carbon that’s already in the atmosphere. Using it to offset continued oil and gas production might slow climate change, but there are a lot of other cheaper, more efficient, and more effective ways to reduce emissions — like switching to carbon-free power and electric cars.
I asked Corless about Smith’s comments later that day over coffee. Was it realistic to double oil production and go carbon neutral? He was coy. It would be very hard, he said. But it also depends on whether you’re talking about neutralizing the emissions from producing the oil versus from burning it. Corless seemed to view the argument as a political necessity, if a dubious one, to win government support for scaling DAC.
“I was hopeful that when the new administration came in, we could create an economic argument and tie what we’re doing to energy dominance and energy security,” he said, of the Trump administration. “It was just, I think, a bridge too far. Whereas here, that narrative is landing.”
Petre was more equivocal, responding that Deep Sky acknowledges that “we are not going to move away from oil and gas tomorrow,” and takes this as motivation to “get direct air capture to as low cost as possible and as easy to deploy as possible.”
In addition to the five DAC units currently installed at Alpha — SkyRenu, Airhive, CarbonCapture, Mission Zero, and a system from a German company called Phlair — Deep Sky has announced plans to bring two more units to the site from Skytree and GE Vernova. A few other deals are in the works but not yet public, Petre told me.
Even once Deep Sky Alpha has enough capacity installed to be printing carbon credits by the day, it won’t have proven that DAC is viable at scale. It’s not meant to. Many aspects of the facility are intentionally inefficient because of its nature as a testing ground.
“We had to do a lot of overspec-ing and oversizing of things,” Petre said. All the excess makes her optimistic about Deep Sky’s next project, however, where it will scale up a smaller number of systems to a much larger capacity. “If we can do something this complex, there’s a lot of room to simplify,” she said.
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Facing down a sea change, the automaker has staked its next EV bet on a compact, sporty pickup.
“Full fathom five, your father lies,” the invisible spirit Ariel sings early in The Tempest, as a handsome and grieving prince listens, rapt. The song tells of a shipwrecked skeleton transforming into something else — its eyes have become pearls, and its bones pink coral — as it undergoes, yes, a “sea change.” It is the first time that phrase appears in the English language.
Ford is now facing its own kind of sea change. Over the past decade, the automaker has doubled down on its most profitable and exciting vehicles — pickups, SUVs, and the Mustang muscle car — and dropped from its line-up the cheap, boring cars that once made it famous. It embraced, then backed off, the transition to electric vehicles, in part because it failed to make money from them; and it began to reckon with the surge of cheaper, cleaner, and “far superior” EVs from Chinese producers that are transforming global auto markets around the world.
Locked into its aging but reliable line-up, yet unable to innovate at the low end, Ford might seem like the epitome of a company facing disruptive innovation. No wonder its stock has traded flat from where it was five years ago — even as the broader market has surged by more than 70%.
Its solution is an EV skunkworks, run by Tesla alumni, where it can develop a new “universal EV platform” to undergird future vehicles. Today, we got a peek at the first car to emerge from that secret shop: an all-electric compact pickup that will hit the roads by the end of next year. Its name? The Ford Fathom.
We know very little about the Fathom, as our correspondent Andrew Moseman wrote today. It will retail for just over $28,000, and even with mandatory delivery costs and other add-ons will stick to this side of $30,000. That makes it only a smidge more expensive than the gas-burning Ford Maverick, a sporty, compact, and popular pickup that starts around $27,000.
Ford promises that the Fathom will have as much seating capacity as Toyota’s RAV4, America’s best-selling car that isn’t a truck. (Ford’s own F-150, of course, holds the true No. 1 spot.) Those dimensions suggest the Fathom will sport a four-door crew cab, like the Maverick, making it more acceptable to families with kids — or young professionals who want to give their friends rides on the weekend. It will also have a frunk.
Beyond that, though, we don’t know much. We don’t know its range, for instance, and its price point shouldn’t inspire too much confidence on that front. Nor do we know, frankly, whether Ford can pull it off: When the automaker announced its first electric truck, the F-150 Lightning, in 2021, it claimed a price point of less than $40,000. Eighteen months of inflation later, it actually sold them for closer to $55,000 — and it still lost money on every EV that it made. Fixing the latter problem is part of why the skunkworks exists in the first place, and Ford now has an additional half-decade of experience making EVs. But consumers hoping for a miraculously priced electric pickup from the Blue Oval have been burned before.
If the Fathom disappoints, though, then consumers will soon have other options. The American car market is about to be deluged with sporty, compact pickup trucks — a welcome change from just a few years ago, when the segment was almost entirely dominated by mid-size and half-ton models. The Jeff Bezos-backed startup Slate will start delivering two-door, all-electric pickups starting at $25,000 at the end of this year. The automaker Stellantis, which owns the Dodge and Jeep brands, says it wants to bring another compact pickup — it’s almost more of a ute — called the Rampage to North America soon.
That’s welcome news for me — I love these little trucks — but I’m a little worried I’ll be outside my pickup-buying years by the time they actually make it to market. In the meantime, I’ll keep you posted on other updates about the Fathom. Will “sea nymphs hourly ring its knell”? No, but it will have Apple CarPlay and Android Auto.
The company confirmed its plans to market research company Cleanview.
The data center buildout has hit a new inflection point. It has long been true that artificial intelligence is fueling climate change by driving up power demand; more recently, tech companies have started directly financing new natural gas plants in their quest for AI glory. Now one is backing the biggest fossil fuel-fired power plant ever to exist in the United States — exclusively to power an AI data center complex.
That company is Amazon, according to the market research company Cleanview, which reported on Friday that the tech giant is building an AI data center campus in Texas powered by an up to 7.65-gigawatt off-grid natural gas plant.
That’s larger than any other power plant in the country — fossil or otherwise. The next biggest plant is the Grand Coulee hydroelectric plant in Washington State, at 7 gigawatts, followed by Arizona’s 4-gigawatt Palo Verde nuclear plant, and the West Count Energy Center, a 3.7-gigawatt natural gas plant in Florida.
The new power plant’s developer, Pacifico Energy, announced in January that it had secured permits from Texas regulators for the project, dubbed “GW Ranch.” The site is also permitted for up to 750 megawatts of solar and 1.8 gigawatts of battery energy storage.
It was not clear who the customer for all this energy would be until earlier this week, when Cleanview uncovered construction permits Amazon filed showing that the company owned the GW Ranch site. The company confirmed to Cleanview that it acquired the site and planned to buy power from Pacifico’s plant.
Not only will this natural gas plant be larger than the one in Florida, it will also use far less efficient technology. Pacifico’s permit says it plans to build 35 “simple cycle” generating units, which are typically installed in rarely-used peaker power plants and waste a lot more fuel potential than the modern “combined cycle” natural gas plants that serve as baseload power for the grid today. These more efficient turbines are essentially on backorder for years, and power-hungry developers have increasingly turned to the simpler versions as a quick fix as they race to bring facilities online.
According to its permit, the GW Ranch plant is allowed to emit as much as 33 million tons of CO2 per year. That’s twice as much as the most-polluting power plant in the country, the James H. Miller Jr. coal plant in Alabama, emitted in 2023, the most recent year for which data is available.
In a statement to Cleanview, an Amazon spokesperson said the company “believes in paying the full costs of powering our operations,” and that this Texas project “does just that: it’s powered by new on-site generation that won’t raise electricity costs for Texas families and designed to transition to grid-connected service as interconnection timelines allow.”
Some researchers disagree on that point, however. In an opinion piece for Utility Dive, Energy Innovation director Jeffrey Rissman and senior fellow Eric Gimon argue that the proliferation of off-grid natural gas generation for data centers will increase costs for regular people more than if the data centers connected to the grid, because they will be competing with utility companies for gas supply. “Data centers can buy gas in bulk and sign long-term contracts (as we’ve seen in Texas, Pennsylvania and New Mexico), giving them access to cheap gas, even if this unfairly drives up prices for everyone else,” they write.
Jane Flegal, a senior fellow at the Searchlight Institute, has also argued that building off-grid natural gas plants to serve data centers locks in emissions for decades because the plants don’t face competitive pressure from other resources. When a new natural gas plant is hooked up to the grid, by contrast, there’s a far greater chance that cheaper, cleaner resources will displace its generation over time.
The Rhodium Group recently developed a scoring system to help investors differentiate between projects that are likely to accelerate the energy transition, those that will have little effect one way or the other, and those that will actively slow it down. They used it to assess options for powering data centers, and found that off grid natural gas plants scored the worst, falling at the bottom of the latter category.
Regardless, Amazon still, somehow, asserts that it is committed to achieve net zero emissions by 2040.
The smoke pouring into Seattle from Spokane is particularly bad, but there’s also no such thing as good smoke.
I wrote this story from inside a cloud of smoke. Owing to some funky meteorology in the Seattle area this week — a pressure ridge paired with a thermal trough — the region’s usual westerly winds reversed, causing smoke from the fires burning in the eastern half of the state to pour through the mountain passes and river valleys of the Cascades and pool over the populous Puget Sound lowlands, where I live.
Though it’s cleared up some today, I’m still running my air purifier on full blast because I know what’s in the lingering smoke. Unlike the still blazing wildfires in Ontario that are burning through mostly uninhabited forests, the smoke in the Seattle area this week came to us partially from Spokane, where the Old Trails fire razed at least 700 buildings and homes last weekend. That means that beyond the usual organic matter associated with wildfire smoke, the pollution that has hung over Seattle has likely also contained particles and chemicals from burned plastics, batteries, cars, and household appliances.
But how can the average person be sure whether their wildfire smoke is the bad kind or the worse kind? (At least assuming that well-adjusted people do not obsessively watch the animations on AirNow.Gov, as I do.) I turned to Coty Jen, an associate professor of chemical engineering, and Albert Presto, a research professor of mechanical engineering, both of Carnegie Mellon University, to learn more about the chemistry of wildfire smoke.
“There is no safe smoke,” Jen said, setting me straight immediately. “It’s all bad. It will piss your body off.”
While it’s true that some smoke is more toxic than other smoke, what you might call the “all natural, organic” variety will still spike hospital emission rates and exacerbate pre-existing respiratory diseases, even if it is mostly burning trees.
Under ideal conditions, when cellulose or lignin — the main structural components of trees and plants as well as leaf litter and soil, the largest sources of carbon during a forest fire — heat up and combust, the chemical reaction creates carbon dioxide, water, heat, and light. But wildfires don’t burn cleanly, and the chemical reactions often stall midway through that process due to things like oxygen availability and temperature variation, producing intermediate products like carbon monoxide or partially broken-down bits of carbon, often called soot. The tiniest of these particles can be smaller than 2.5 micrometers across — 30 or more could fit across the width of a human hair — and are measured collectively as PM2.5, a catch-all term that refers to the size of the particle rather than what it is. What’s important, though, is that these particles are small enough to penetrate deep into our lungs and potentially enter our bloodstream, factors that add to the known mortality associated with PM2.5 exposure.
Different kinds of forests create different emissions — heavy duff, or leaf litter, which is common in pine forests, creates some of the densest smoke conditions. Wetter fuels also burn “dirtier,” creating more pollution. Different topographies also impact air quality in myriad ways; it’s no surprise that some of the worst pollution from the Spokane wildfires pooled in mountain valleys as a warm overhead layer of air trapped the particles near the ground.
Even “natural” wildfires can be extra toxic; burning eucalyptus, which grows in Southern California, is not something you want to inhale. Pine smoke can cause mutations in bacterial DNA, a common lab test for a substance’s potential to cause cancer. Wildfires that smolder are worse than those that burn fast; researchers have found that PM2.5 can be up to 70 times higher when fuels aren’t actively on fire. “You can even see this if you’ve ever built a fire yourself,” Presto explained. “There’s a period where everything is big and flaming, and then, if you’re burning a log, it eventually goes down to smoldering. The emissions are different.”
In the case of something like a house burning down in a wildfire, however, it’s not only cellulose and lignin combusting. “We’re good at engineering materials that are extremely robust, but when they burn, they release very exotic compounds,” Jen said. She pointed to the common plastic PVC, which is used for everything from exterior siding to plumbing and window frames. When it combusts, PVC releases chlorine, “which is very bad for you,” Jen told me. “It’s like how bleach is bad for you — it’s a pretty nasty chlorine compound. PVC isn’t releasing bleach, but it is releasing radical chlorine molecules that produce some crazy compounds.”
If you’re following a smoke event at home, the answer is “not really.” PM2.5 is measured in micrograms per cubic meter, which tells us how much small stuff is floating around, but not what that small stuff is. “It is pretty difficult to measure all the different compounds that wildfires, or broadly any pollution, will emit,” Jen said. “The easiest way to quantify it is to literally suck air onto a filter and measure how heavy it got.”
Measuring what exactly is in that mass requires instruments that cost in the ballpark of half a million dollars, which is not financially feasible at every air monitoring station, Jen went on. But while there are certainly academic applications for that kind of knowledge, a person trying to decide whether or not to go for their run in wildfire smoke doesn’t need that level of granularity.
“Some smoke is definitely more dangerous,” Jen said. “But as innocent bystanders, it’s not like we can pick and choose what smoke floats over to us. You just have to live with it, so the best mentality is to treat all smoke as bad.”
In a 2026 Science Advances study that attributed more than 24,000 deaths per year to wildfire smoke in the U.S., researchers found no safe threshold for PM2.5 exposure. Every 0.1 microgram per cubic meter increase in a county’s average annual PM2.5 from smoke was associated with nearly 5,600 excess deaths nationwide, even though most counties saw only trace amounts of smoke — about 0.4 micrograms per cubic meter a year. While it’s “orange sky” days, when the pollution spikes into triple-digit AQI numbers, that get the most media attention, even low exposure that you can’t smell or even see can be affecting your health.
PM2.5 is just one component of wildfire smoke — the other is gases, including benzene and formaldehyde. Many gases chemically transform as they move from where the fire is to where you inhale them. “The atmosphere is extremely oxidizing — it likes to add oxygen molecules onto compounds,” Jen said.
Some of those compounds react faster than others, “so it depends how downwind you are,” Jen went on. That’s why people closer to a wildfire — maybe a day or less downwind — get the distinctive campfire smell, mainly from the “young” vapors and volatile organic compounds. But for people on the East Coast who were subject to the Ontario smoke several weeks ago, the smoke had to travel several days to reach places like Pittsburgh and New York, and by then the sharper-smelling compounds had transformed into new pollutants like ozone.
The AQI only measures a few specific gases that are considered “criteria pollutants” under the Clean Air Act, which means, as Presto told me, “during these fires, you could emit a whole bunch of different other gases that don’t have an AQI number.”
Instead, you can look at the PM2.5 number to get the gist of how prevalent wildfire gases are. “If your PM 2.5 is high, it’s impossible for the bad gasses to be low,” Jen said. “The way we think about it is, there’s a bunch of junk on the particle, and if the same junk’s not also in the gas, it will evaporate off the particle into the gas. They always exist together.”
You might notice by now that I’ve written little about the actual AQI number, that score that appears on your weather app and runs from zero to 500 (or, confusingly, even higher). That’s because while the AQI is a great communication tool, it doesn’t offer us much in the way of the science of wildfire smoke.
The AQI measures five different pollutants — PM2.5, ozone, carbon monoxide, sulfur dioxide, and nitrogen dioxide — with the EPA setting specific concentration thresholds for each one, as my colleague Emily Pontecorvo has explained. “If local concentrations of any one of them tick up above those protective standards, the AQI will jump from green to a more alarming color,” she wrote. “The higher the level of pollution is, the higher the AQI and the darker the color will be.”
If you want to impress your friends, though, you ought to zero in specifically on the PM2.5 concentration — again, because the prevalence of the tiniest particulates is a good indicator of all the other gunk you can assume is in the air, too. (You can find the specific PM2.5 concentration usually by clicking for more information about the AQI on your weather app or checking IQ Air’s widget.) For example, at the time of this writing, my local PM2.5 concentration is 50 micrograms per cubic meter, more than triple the World Health Organization’s 15 micrograms per cubic meter threshold for 24-hour exposure. (The EPA’s 24-hour threshold is much more lenient, at 35 micrograms per cubic meter.)
When I asked Jen how she stays sane knowing all she knows about smoke exposure, she laughed. “I have just generally become more terrified of all campfires and all barbecues, but people already think I’m weird, so I might as well add to it,” she told me.
In all seriousness, though, she told me the answer is air filters, and her confidence in their ability to work. When wildfire smoke rolled through Pittsburgh, she had two running that she moved from room-to-room with her family, as well as a whole-house air filter. “We were getting PM2.5 concentrations in our house of about 80 micrograms per cubic meter when it was 150 outside,” she said. “But with the air filter on, we could drop that down to less than eight.”
Jen pointed out, though, that many people do not run their air filters properly. Filters are rated at their highest blower level, “so for them to be effective, you need to crank them to their highest setting to get all the air through,” she said. Most people keep their filters on auto or low because they’re so loud — myself included, until I learned otherwise.
Additionally, while an air filter is a rather large appliance, it really ought to be placed in the center of your room to be the most efficient, rather than up against a wall. (Again, my bad.) “When these wildfire events happen, the most effective place for the air filter is where you are, and you have to run it loud, which kind of sucks,” Jen said. “But it is better than breathing in gross air.”