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Is it safe to turn it on an AC? If you have an air purifier, where should you put it? An air quality expert answers our pressing questions.

You’re in your apartment, windows closed, hiding out from the wildfire smoke blanketing your city. But it’s starting to smell a little bit like barbecue, and your eyes are getting watery. What should you do?
Wildfire smoke contains tiny particles, invisible to the human eye, that can enter your lungs and bloodstream. Those particles can exacerbate the risk of having an asthma attack, heart attack, and stroke. They also have lasting effects on your heart and respiratory system, and can lead to premature death. You really want to take the likelihood that smoke is getting into your home seriously.
But that can lead to a lot of questions.
Maybe you have an air purifier. Where should you put it?
Maybe you don’t have an air purifier, but you have a window air conditioner. Is it safe to turn it on?
I called up John Volckens, a professor of mechanical engineering at Colorado State University, and grilled him on every home configuration I could think of to understand how you can protect yourself against the dangers of smoke. Volckens studies air quality, exposure science, and air pollution-related disease. He has even pioneered the development of new pollution sensor technologies. He had a lot of helpful tips to offer.
It’s important to understand there’s really no way to fully prevent smoke from getting inside your home. Even if you don’t smell it or feel its effects, you should do what you can to protect yourself.
That’s because most homes and buildings “breathe.” As the sun heats the upper reaches of the building, it warms the air, which expands and wants to escape. As the air flows out, the lower part of the house, where it’s cooler, draws new air in to replace it.
“The analogy would be like if a 6-foot flood of water came to your house. It doesn’t matter how many sandbags you have, the water’s coming in, right?” Volckens said. “If the air quality index is like 400 outside for a few hours, it’s going to get to like 200 inside your home no matter what.”
The number one thing you can do is get an air purifier. You might not be able to find one in stores right now or have one delivered in time, but there are other options, too, as I’ll discuss below.
Place it wherever you are.
We spend a third of our lives in bed, so Volckens said he likes to have one in the bedroom. “If you have seasonal allergies, creating that kind of safe space for your immune system can be really helpful,” he told me.
But if you only have one device, when you’re done sleeping, just pick it up and move it into the kitchen, office, or living room with you. It should only take about an hour to work its magic and get whatever room you’re in to the best air quality that it’s capable of.
Window AC units work by recirculating the air in your apartment, so they won’t exacerbate the issue and are generally safe to use. The filters in your window units won’t do much to improve your air, though — they are designed to catch larger particles like dust and animal fur, and smoke particles will slip right through.
If you have a central air conditioning system that delivers cool air through ducts and vents, that’s another story. Those are typically designed to draw in air from the outside. In that case, the best thing to do is install what’s called a MERV filter, which you can purchase at most hardware stores or big box stores. Volckens recommends picking up a filter rated MERV-13, which can capture the smallest particles at a relatively high rate.
“It will probably be like 75% efficient. So if 100 wildfire smoke particles pass through that filter, only 25 will get through,” he said. “You're going to knock down the concentration significantly, especially as that filter keeps cycling air through your home.”
The one thing to keep in mind is that these filters are so good, they will get clogged quickly. A clogged filter will cause your HVAC system to work too hard, which could lead to mechanical issues, so make sure you remember to replace it every couple of months.
What's the alternative to an air purifier?
DIY air filters are surprisingly easy to make and incredibly effective. No, really. All you have to do is buy a box fan, duct tape, and a MERV filter. Tape the filter to the back of the box fan. That’s it.
“They work just as well as commercial air cleaners,” said Volckens. They’re a little bit louder, but otherwise, it’s the exact same idea. “A commercial air purifier might have a fancier fan and a fancier filter, but it’s still just a fan and a filter.”
And if you want to get a little fancier, you can build what’s called a Corsi-Rosenthal box. It’s the same idea, but envelops the fan intake in four filters instead of one. The Washington Post has a very easy-to-follow video showing how to build one. “They work as best as the highest-end air cleaners you could buy for one-fifth or one-tenth of the cost,” said Volckens.
N-95 masks, like the kind recommended to protect against COVID-19, also effectively filter out pollution, and are your best bet. Even a blue surgical mask will be somewhat helpful, said Volckens.
If you’re tired of being cooped up at home, you can also find what Volckens likes to call “clean air zones.” He recommended the public library, a Starbucks, or any other public building. Go support your local movie theater.
“Most public buildings actually have more efficient air cleaning than homes because the buildings were built more recently and they’re built to code standards that require cleaner air.”
Wildfire smoke is truly disgusting. The particles can contain thousands of chemicals, and they will stick to any surface they touch — the ceiling, the carpet, your clothing. You can certainly wash your clothes and linens, but it might not be possible to scrub every surface of your home.
“The best thing you can do when the air does clean up is to just open all your windows and get some good air exchange going,” said Volckens. “I guarantee, yes, you’ll have that wildfire smell for a couple of days, but it will eventually go away.”
Before we hung up, I asked Volckens if there were any other tips we didn’t cover.
“The only thing I’ll say is that this problem isn’t going away,” he said. “And it’s our doing, right? This is the result of a warming planet.”
This article was last updated on June 28, 2023.
Read more about wildfire smoke :
The 5 Big Questions About the 2023 Wildfire Smoke Crisis
Wednesday Was the Worst Day for Wildfire Pollution in U.S. History
When There’s Smoke, Getting Indoors Isn’t Enough
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Microsoft says it bought nearly 3,500 acres of land near Cheyenne from the family of Wyoming Senator Cynthia Lummis.
The family of one of Congress’ biggest Big Tech boosters has reportedly sold thousands of acres of land to Microsoft for a new data center.
Late Monday night, the city council in Cheyenne, Wyoming approved a measure necessary for Microsoft to connect a new data center campus to city services, including water access. The council’s action annexes almost 3,500 acres that was owned by relatives of the state’s junior senator, Cynthia Lummis. A Microsoft representative testified to the council that the company acquired the land on June 26.
Honestly, it’s a surprise that the land annexation — reportedly one of the largest single additions of land to the city’s control in its history — was even approved. Just last week I confirmed local reports that officials had traced rare bacteria in the city’s municipal wastewater system to another data center project overseen by a subcontractor for Meta. This incident led the city to ban data center developers indefinitely from disposing wastewater from closed-loop cooling systems into the municipal wastewater system.
The land annexation was approved in the wee hours of the night by a 7-3 vote, after a nearly eight-hour marathon session of the city council that also included other much smaller land swaps for the Microsoft project. The state representative for the area where the property sits, Republican Ann Lucas, testified against the measure. Many Cheyenne residents who spoke in opposition to the project referenced the Meta-linked incident, and a handful of neighbors of the future data center complex got together to testify against it.
“I oppose this annexation, but I understand that Senator Lummis has a right to request it, just like she did for the land that my house is on,” testified Peggy Gates, who lives in a residential community called Sweetgrass that is adjacent to the property. “My sincere question to the city council is, why is it necessary for this annexation and rezoning vote to be completed tonight?”
Patrick Collins, Cheyenne’s mayor, told her the city faced a choice: either move forward with an annexation that would put the property under its control and let it connect to municipal services, or Microsoft would have to go its own way under solely county control.
“It’s a good question,” Collins replied from the dais. “I would guess if we postponed it for three months, people would say we should postpone it longer. At some point we just have to vote and say yes or no and give the people who want to develop that piece of property clearer direction of whether they can be in the city or not in the city. They already own the land. They’re either going to do it in the city or outside the city. We’re trying to give them direction as to how they should make their plan. Should they drill [water] wells or use city water and sewer?”
How much money the Lummis family may make from the data center land deal has not yet been made public, nor have the ways in which the senator or her family could profit. The family has reportedly held much of this land going back to the 1940s, and it now sits in the name of companies such as Arp and Hammond Hardware, Old Horse Pasture Inc., and Lummis Livestock Company LLC.
As far as I can tell, this is the first major data center deal ever involving a sitting member of the U.S. Congress. Lummis is also the “crypto queen” of the Senate, known as a policy thought leader in all things technology, artificial intelligence, and the digitization of human existence. She’s recently waded into the data center debate: In mid-June, after Microsoft disclosed its intent to acquire the Lummis properties, the senator introduced a bill requiring the Federal Energy Regulatory Commission to quickly craft new regulations making it easier for data centers using 100 megawatts or more to connect to the existing electrical grid.
Lummis announced in December that she will not be seeking re-election. Her office did not respond to requests for comment.
Microsoft told me in a statement that the senator’s connection to this land played no role in selecting this site for their project: “This expansion reflects our continued long-term investment in Cheyenne and builds on more than a decade of growth in the region. Senator Lummis’ political standing had nothing to do with our decision to continue growing in Cheyenne,” the company said.
“Geologic hydrogen” companies make up a hefty portion of the latest Activate Fellowship class, announced Tuesday morning — a reliable harbinger of investments to come.
The hype around clean hydrogen has come in waves, with investors and policymakers betting that the versatile molecule could help decarbonize everything from fertilizer production to long-haul shipping and heavy industry. Different production methods have come in and out of vogue: Around 2020 it was using carbon capture and storage, then electrolysis powered by clean electricity and subsidized by generous tax credits in the Inflation Reduction Act. More recently, venture capitalists have poured money into the search for naturally occurring deposits hidden underground.
So far, none of these approaches has delivered cheap, low-carbon at any kind of scale. Yet enthusiasm for this latest frontier — so-called geologic hydrogen — has continued to build.
Much of that excitement stems from an even newer concept, alternately known as engineered geologic hydrogen or engineered mineral hydrogen. This is the idea that if naturally occurring hydrogen deposits — which require a precise mixture of geologic conditions — prove too rare or difficult to find, scientists can engineer those subsurface conditions themselves, producing this valuable molecule straight from the earth wherever the right iron-rich rocks are found. Essentially, the approach trades exploration risk for engineering risk.
“I think it’s really a natural evolution,” Sophie Broun, CEO of the seed-stage engineered hydrogen company Anning Corporation, told me. “It’s the evolution that we’ve seen play out from oil and gas — conventional to unconventional — from geothermal to [enhanced geothermal systems], and now we’re seeing it in geologic hydrogen.”
Broun is a member of the new class of Activate Fellows announced on Tuesday morning. The two-year fellowship provides early-stage founders with funding for research and development, as well as a network of fellow founders, mentors, investors, and corporate partners. It’s helped seed cohorts of companies that have gone on to form brand new industries, from clean cement startups Brimstone and Sublime Systems to thermal energy players Antora Energy and Electrified Thermal Solutions.
Dan Recht, Activate’s chief fellowship officer, thinks that the nascent geologic hydrogen industry — which includes both natural and engineered deposits — is next. “This process of seeing these up and coming sectors and industries is routine for us at Activate,” he told me. “At the end of our selection process we now have a pretty good sense of, oh, the U.S. is going to have a geologic hydrogen industry.”
Of the 50 fellows selected this year, nine work in energy. Of those nine, three are hydrogen companies: geologic hydrogen startups Anning and Hydrify, as well as Brint Tech, which is developing hydrogen leak detectors. Anning is squarely an engineered hydrogen company, aiming to stimulate the production of the molecule underground using an undisclosed technology, while Hydrify is building tools to better locate where natural hydrogen deposits already exist.
Like Broun, Recht sees a clear parallel with the geothermal industry, where Fervo Energy is manipulating the subsurface to create the conditions necessary for geothermal power production and Zanskar is using artificial intelligence models to identify previously overlooked conventional geothermal resources. Anning could become the Fervo of hydrogen, while Hydrify could be its Zanskar, he told me. The parallels also extend beyond the companies themselves: The drilling techniques that underpin geothermal development — largely adapted from the oil and gas industry — stand to be just as critical to unlocking geologic hydrogen, which could give this emerging tech a similar bipartisan appeal.
Natural hydrogen company Koloma is by far the best capitalized startup in this space, having raised around $400 million from big-name backers such as Breakthrough Energy Ventures, Amazon’s Climate Pledge Fund, and Khosla Ventures. That said, it has yet to publish any results indicating it’s discovered commercially significant new deposits. That relative silence from the industry’s biggest player has helped fuel the dreams of the even-more-nascent engineered players such as Anning, Vema Hydrogen, Addis Energy, GeoKiln and Eden GeoPower, who think they can achieve quicker, more consistent breakthroughs.
“By being able to deploy the engineered solution, we’re able to be repeatable and scalable, and ultimately, that’s what customers and infrastructure providers need,” Broun told me. Being able to produce hydrogen closer to where it’s actually used could slash transportation costs, often one of the most expensive parts of the hydrogen value chain as the gas typically must be compressed or liquified before transport. “Being able to place that engineered system at a location that’s much more within your control, I think that that is a far stronger or more appealing business case in many cases,” she explained.
Anning raised a pre-seed round last year, and is now raising a $6 million seed round, which would put it more or less on par with other early players in the engineered hydrogen subsector. Vema has raised the most thus far, bringing in an oversubscribed $13 million seed round last February from a group of climate-focused investors including Extantia Capital and Propeller, and is now raising its Series A.
Vema drills its wells into iron-rich rock formations known as ophiolites, then injects water and a proprietary catalyst to trigger serpentinization, a natural geochemical reaction between water and iron minerals that produces hydrogen gas. While this process would typically unfold over millions of years, Vema says it’s aiming to speed up that reaction by a factor of 10,000 to generate commercial quantities of hydrogen on a human timeframe. The resulting hydrogen gas would then flow back to the surface through the well, where it would be purified before its delivery to customers.
The company’s senior vice president of operations, Colin McCulley, told me he expects that it can all be done for less than $1 per kilogram, the so-called “magic number where you start to compete with petroleum-derived hydrogen.” And Vema’s CEO, Pierre Levin, told TechCrunch that once the startup dials in its tech, the price will eventually drop to less than 50 cents per kilogram, making it definitively the cheapest form of hydrogen yet developed.
The company is currently conducting pilot testing in Quebec, home to the well-mapped Thetford Mines ophiolite deposits. But while Vema has yet to release any early results from this pilot, it’s already laying the groundwork for rapid commercialization. Late last year, Vema signed a conditional 10-year offtake agreement with the off-grid data center power startup Verne to supply up to 36,000 metric tons per year of hydrogen, with delivery expected to begin “as soon as 2028.” Then last week, the startup inked a nonbinding memorandum of understanding with Montreal-based sustainable aviation fuels developer SAF + International Group to supply 4,000 tons of hydrogen annually, also beginning “in approximately 2028.” The group will make that fuel at a facility co-located with Vema’s planned Quebec production site to minimize transport costs.
A report shared with me last month from the Cleantech Group, a San Francisco-based market intelligence and advisory firm, cast some doubts on that timeline, however. It called the 2028 target “over aggressive,” given that Vema will need to build a first of its kind facility to fulfill its deals with Verne and SAF + International Group.
“This is the Earth. This isn’t like your lab space where you can exactly control the pressure and temperature and conditions that exist downhole,” Diana Rasner, author of the report and the firm’s group lead for materials and chemicals, told me. “You’re going into territory you can’t see, or that you don’t know how it behaves day to day, let alone like on the scale of what you would think hydrogen production needs to be.”
Even McCulley admits that it’s a stretch, telling me that, “If we have realistic complexity in our project, it will be difficult to deliver on this timeline.” But he thinks the ambition is essential to demonstrate near-term demand and secure commitments for larger projects down the road. He expects the industry to really hit its stride between 2035 and 2040, by which point he says Vema could be looking at a fourth or fifth large-scale commercial project at costs competitive with fossil fuel-derived hydrogen.
But Vema is now facing competition from startups pursuing markedly different approaches to the same problem. Because heat is a natural accelerant of serpentinization, a company called GeoKiln is forgoing chemical catalysts altogether in favor of underground electric heaters designed to stimulate and speed up hydrogen production. Meanwhile, Eden GeoPower plans to apply high voltage electricity to fracture surrounding rocks, which also releases heat and exposes fresh reactive rock surfaces.
Then there’s Addis Energy, which is betting that ammonia production offers a stronger commercial proposition. Hydrogen is often an intermediate molecule in the process of producing ammonia, which is widely used in fertilizers and has become newly interesting for low-carbon shipping fuel. Addis aims to skip that conversion step entirely by injecting water, its own proprietary catalyst, plus a nitrogen-containing compound into the subsurface, triggering a chemical reaction that directly produces ammonia — a molecule that’s simple to transport using existing shipping infrastructure.
Eden raised a $12 million seed round in 2023, backed by a mix of oil and gas industry investors and sustainability-focused funds, while Addis raised a $8.3 million seed round late last year led by climate tech VC At One Ventures.
But investing in the space, Rasner told me, isn’t something everyone in the VC community is comfortable with these days. “It’s not to say that they didn’t believe in it,” she said of investors who did eventually pull the trigger. But it certainly wasn’t an easy decision. As promises of affordable, low-carbon hydrogen production have come and gone, there’s an undeniable aura of uncertainty around the industry, a feeling that has only grown stronger since the Trump administration curtailed clean hydrogen subsidies and froze funding for the previous Biden administration’s hydrogen hubs initiative.
With natural hydrogen players such as Koloma yet to deliver on their early momentum, Rasner told me many would-be backers are approaching the sector with a general attitude best summarized as, “You’re going to be able to do the thing that a lot of the big names in this space haven’t been able to prove out yet, but on your own terms? What’s the catch?”
Recht, however, naturally has a more optimistic outlook. The subsurface has long supplied the minerals that underpin our modern economy, and now it’s increasingly being tapped for geothermal energy as well. In his view, it’s only natural that it might be able to deliver the long-promised hydrogen economy.
“It turns out we’re really good at digging stuff up out of the ground cheaply. If you look at what has humanity decided to do with the past century, it’s to get good at that.”
Current conditions: New England is bracing for a series of severe thunderstorms this afternoon with the potential to cause widespread damage from winds and flooding • A firefighting helicopter crashed while battling Colorado’s Gold Mountain Fire, killing the pilot • Temperatures in Delhi, India, are nearing 100 degrees Fahrenheit today.
Dubai is planning to build a new port and container terminal on the United Arab Emirates’ east coast in a bid to circumvent the Strait of Hormuz and neuter Iran’s ability to leverage its control of the waterway toward geopolitical ends. On Monday, the Financial Times reported that DP World, the logistics giant and port operator based in the glitzy Emirati megacity, was working on a new port in the coastal area of Fujairah. The company’s Jebel Ali hub, located near the contested maritime route, has long served as “Dubai’s crown jewel.” But the newspaper said “shifting some of the port’s capacity outside Dubai marks a seismic change for the emirate, which has established itself as a global trade and finance hub partly off the back of Jebel Ali’s growth.” After all, activity at the port nosedived by as much as 95% after the United States and Israel began bombing Iran in February.
Meanwhile, the war appears to be back on. After resuming mutual attacks last week, President Donald Trump said Monday the U.S. would reinstate its blockade of Iran’s ports. “The U.S.A. will be, from this point forward, known as ‘THE GUARDIAN OF THE HORMUZ STRAIT,’” Trump wrote in a post on his Truth Social network.
With the world’s largest fleet of nuclear reactors, the U.S. has the capacity to pump out about 97 gigawatts of atomic energy. If every project now waiting in the pipeline goes forward, the country could nearly double that total capacity. A new analysis by the Breakthrough Institute, a think tank, found that the U.S. has 74 gigawatts of projects in various stages of development. “While it is unlikely that all of that capacity will ultimately be built, if even a fraction of it is deployed it would mark a historic turnaround for the U.S. nuclear industry,” Joy Jiang, an analyst at the Breakthrough Institute who authored the paper, wrote in a blog post. And more appears to be coming: New Jersey Governor Mikie Sherrill signed a bill Monday that creates a new procurement process for building a new nuclear plant in the state.
In Belgium, meanwhile, the government just approved nearly $12.5 million in funding for eight nuclear energy research projects as Prime Minister Bart De Wever seeks to reverse his country’s previous phaseout policy. On Monday, NucNet reported that the government wanted to restore nuclear power to its “rightful place” in the Belgian energy mix.
The International Brotherhood of Electrical Workers, or IBEW, added a record 30,000 new members so far this year, up from 24,000 a year ago. The milestone, announced Monday in a post on X, highlights a looming challenge for Democrats who are embracing the populist wing of the party’s calls for a moratorium on data center construction, no doubt a large part of what’s led to the recent hiring boom. “The building trades unions that the left’s major decarbonization agenda revolves around putting to work are further alienated by data center rejection (instead of regulation),” Fred Stafford, the pseudonymous socialist energy researcher and Heatmap contributor, wrote in a post on X. Still, the political dynamics are hard to pass up for left-wing candidates and advocacy groups. As Semafor reporter David Weigel wrote on X, moderates worry that coming out against a data center will activate opposition spending from the AI industry’s political action committees. “No such worries on the left, which wasn’t getting that money,” he wrote.
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Turkey is building its first nuclear plant and billions of dollars of new hydroelectric dams. But that doesn’t mean wind and solar don’t have a part. On Monday, Renewables Now reported that, over the weekend, the Turkish Ministry of Energy and Natural Resources published announcements for nearly two dozen renewable energy tenders scheduled for this year, with a target of deploying 2.4 gigawatts of new projects.
Shortly after the 2024 presidential election, Heatmap’s Katie Brigham declared “the death of ‘climate tech.’” By that, she meant that the incoming Trump administration would kibosh use of that two-word phrase to describe next-generation technologies that could generate power without emissions or reduce the impacts of global warming in other ways. But the sector is mounting quite a comeback. In the first half of this year, the global climate tech sector notched its busiest six months on record. A Bloomberg write-up of a new analysis by the market research firm Currence identified 153 transactions in the first half of 2026. That’s an eye-popping 70% hike from the same period last year.
It’s been 36 years since the signing of the Americans with Disability Act, yet the country remains tragically inaccessible to people who use wheelchairs, walkers, and canes. (For a disturbing account of just how bad things are in the nation’s largest city, listen to this old “This American Life” episode about lawyer and advocate Britney Wilson’s struggle to use Access-a-Ride, New York City’s para-transit provider.) It’s a problem Tesla aims to change. The auto giant is building a wheelchair-accessible self-driving taxi. But Electrek cautioned that Tesla “gave no timeline, no vehicle, and no details, and it’s not clear the ‘active product’ is anything more than the Robovan it unveiled nearly two years ago.” Nevertheless, I’d welcome its entry to the roads.