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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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Utilities are bending over backward to convince even their own investors that ratepayers won’t be on the hook for the cost of AI.
Utilities want you to know how little data centers will cost anyone.
With electricity prices rising faster than inflation and public backlash against data centers brewing, developers and the utilities that serve them are trying to convince the public that increasing numbers of gargantuan new projects won’t lead to higher bills. Case in point is the latest project from OpenAI’s Stargate, a $7-plus-billion, more-than-1-gigawatt data center due to be built outside Detroit.
The project was announced Thursday by Michigan Governor Gretchen Whitmer, who focused heavily on the projected economic benefits of the projects while attempting to head off criticism that it would lead to higher costs. In the first sentence of her press release, she said that the project will “create more than 2,500 union construction jobs, more than 450 jobs on site and 1,500 more across the county.” Also, it “will be one of the most advanced AI infrastructure facilities in the U.S., especially when it comes to its efficient use of land, water, and power.” Oh, and it “will not require any additional power generation to operate.”
The utility set to power the project, DTE Energy, released its quarterly earnings Thursday, as well, which described a 1.4-gigawatt project it had already executed. In a presentation for analysts and investors, DTE said that the new data center would pay for “required storage through a 15-year energy storage contract,” and that it would “support affordability for existing customers as excess capacity is sold.”
On a call with analysts, DTE Energy chief executive Joi Harris further asserted that the project has “meaningful affordability benefits to our existing customers.” As the data center ramps up, she explained, it can use existing excess capacity on the grid. By the time it reaches full strength, it will enjoy the benefits of “nearly $2 billion of incremental energy storage investments and additional tolling agreements to support this data center load.”
Who will pay for energy storage and tolling agreements? A DTE spokesperson, Jill Wilmot, clarified in an email that “DTE will meet the 1.4 gigawatts of demand from the data center with existing capacity,” and that “new energy storage will be built — and paid for by the customer” — that is, Stargate — “to help augment times of peak demand, ensuring continued reliability for all customers.”
Data centers help spread out the fixed costs of the grid more widely, Wilmot went on. “Data center development in DTE’s electric service territory will not increase customer rates,” she said, adding that “DTE is ensuring the data center will absorb all new costs required to serve them — in this case, battery storage. Our customers will not pay.”
That said, Wilmot did not answer a question about whether there would be any network or transmission upgrades necessary. She told me that she expected DTE would make a filing for the project with Michigan regulators later Friday.
Consumer advocates were skeptical of the utility’s claims. “When you are talking about new demand as massive as what would be created by this data center, we can’t afford to just take DTE at its word that other customers won’t be affected,” Amy Bandyk, the executive director of the Citizens Utility Board of Michigan, told me in an email. She called for Michigan regulators “to require DTE and the data center customer to agree on a tariff specific to that customer that includes robust protections against cost-shifting and provisions that any incremental costs will be solely covered by this new customer.”
More utilities and data center developers are trying to explicitly head off claims that data centers are driving up electricity rates. In another recent data center announcement for a multi-billion-dollar project in West Memphis, Arkansas, Google and the Arkansas Economic Development Commission said that “Google will be covering the full energy costs for the West Memphis facility and will be ramping up new solar energy and battery storage resources for the facility.”
Drew Marsh, the chief executive of Entergy, the utility serving the project, confirmed on an earnings call earlier this week that Google “will protect energy affordability for existing customers by covering the full cost of powering the data center in West Memphis.” He also said that in Mississippi, where Amazon has announced a $16 billion project, “customer rates would be 16% lower than they otherwise would have been due to these large customers.”
So why are utilities — which, after all, get paid by ratepayers for the investments they make in their systems — telling their investors about all the money they’re not charging ratepayers?
In short, utilities and developers know they’re on political thin ice, and they don’t want to kill the golden goose of data center development by stoking a populist backlash to rising electricity prices that could result in either government-mandated slashing of their investment plans, caps on the rates they can charge, or both.
“Looking ahead, we anticipate the central issue will be how utilities protect residential customers from costs associated with large-load customers, or else face potential consequences from regulators,” Mizuho analyst Anthony Crowdell said in a note to clients earlier this week. “Data centers, and their associated load, have the potential” to “cause political push-back.”
This is already happening across the country. The frontrunner in the New Jersey gubernatorial race, Democrat Mikie Sherrill, for example, has promised to freeze electricity rates, which have seen a sharp runup in recent years. Indiana Governor Mike Braun, a Republican, said in a recent statement that “we can’t take it anymore,” in reference to rate hikes. Indiana has also rejected a number of proposed data centers, as I covered earlier this year.
This means that utilities will have to think carefully about how and to whom they allocate costs arising from data center development and operation.
“Allocation of cost will be pivotal as the current ’pocketbook issues driving a lot of the U.S. political debate could create some challenging regulatory outcomes should data centers put pressure on customer bills,” Crowdell wrote.
But what’s said in an announcement to the media or to investors may not always reflect the reality of utility cost allocation, Harvard Law School professor Ari Peskoe told me.
“Don’t trust a utility press release or comment from a CEO of a monopoly that says Hey, these rates are good for you,” he told me.
Peskoe told me to pay close attention to the regulatory fillings utilities make for their data center projects, not just what they tell the press or investors. “Are the utilities themselves actually making these claims as strongly as their CEOs are making them in investor calls? And then once we do have a regulatory process about it, are they being transparent in that regulatory process? Are they hiding a lot of details behind the confidentiality claims so that only the participants in that proceeding actually get to see the details?”
Peskoe also pointed to other costs that might be incurred in the course of data center development that get socialized across the rate base but aren’t necessarily directly tied to any one development, like the transmission and network upgrades, that have contributed to large price increases in the PJM Interconnection territory.
“What you’re looking for is a firm contract that ensures the data center is going to be paying for every penny that the utility is incurring to provide service, so that it’s paying for all the new infrastructure that’s serving it,” Peskoe said. Without that, all you have is a press release.
The state formerly led by Interior Secretary Doug Burgum does not have a history of rejecting wind farms – which makes some recent difficulties especially noteworthy.
A wind farm in North Dakota – the former home of Interior Secretary Doug Burgum – is becoming a bellwether for the future of the sector in one of the most popular states for wind development.
At issue is Allete’s Longspur project, which would see 45 turbines span hundreds of acres in Morton County, west of Bismarck, the rural state’s most populous city.
Sited amid two already operating wind farms, the project will feed power not only to North Dakotans but also to Minnesotans, who, in the view of Allete, lack the style of open plains perfect for wind farms found in the Dakotas. Allete subsidiary Minnesota Power announced Longspur in August and is aiming to build and operate it by 2027, in time to qualify for clean electricity tax benefits under a hastened phase-out of the Inflation Reduction Act.
On paper, this sounds achievable. North Dakota is one of the nation’s largest producers of wind-generated power and not uncoincidentally boasts some of cheapest electricity in the country at a time when energy prices have become a potent political issue. Wind project rejections have happened, but they’ve been rare.
Yet last week, zoning officials in Morton County bucked the state’s wind-friendly reputation and voted to reject Longspur after more than an hour of testimony from rural residents who said they’d had enough wind development – and that officials should finish the job Donald Trump and Doug Burgum started.
Across the board, people who spoke were neighbors of existing wind projects and, if built, Longspur. It wasn’t that they didn’t want any wind turbines – or “windmills,” as they called them, echoing Trump’s nomenclature. But they didn’t want more of them. After hearing from the residents, zoning commission chair Jesse Kist came out against the project and suggested the county may have had enough wind development for now.
“I look at the area on this map and it is plum full of wind turbines, at this point,” Kist said, referencing a map where the project would be situated. “And we have a room full of people and we heard only from landowners, homeowners in opposition. Nobody in favor.”
This was a first for the county, zoning staff said, as public comment periods weren’t previously even considered necessary for a wind project. Opposition had never shown up like this before. This wasn’t lost on Andy Zachmeier, a county commissioner who also sits on the zoning panel, who confessed during the hearing that the county was approaching the point of overcrowding. “Sooner or later, when is too many enough?” he asked.
Zachmeier was ultimately one of the two officials on the commission to vote against rejecting Longspur. He told me he was looking to Burgum for a signal.
“The Green New Deal – I don’t have to like it but it’s there,” he said. “Governor Burgum is now our interior secretary. There’s been no press conferences by him telling the president to change the Green New Deal.” Zachmeier said it was not the county’s place to stop the project, but rather that it was up to the state government, a body Burgum once led. “That’s probably going to have to be a legislative question. There’s been nothing brought forward where the county can say, We’ve been inundated and we’ve had enough,” he told me.
The county commission oversees the zoning body, and on Wednesday, Zachmeier and his colleagues voted to deny Longspur’s rejection and requested that zoning officials reconsider whether the denial was a good idea, or even legally possible. Unlike at the hearing last week, landowners whose property includes the wind project area called for it to proceed, pointing to the monetary benefits its construction would provide them.
“We appreciate the strong support demonstrated by landowners at the recent Commission meeting,” Allete’s corporate communications director Amy Rutledge told me in an email. “This region of North Dakota combines exceptional wind resources, reliable electric transmission infrastructure, and a strong tradition of coexisting seamlessly with farming and ranching activities.”
I personally doubt that will be the end of Longspur’s problems before the zoning board, and I suspect this county will eventually restrict or even ban future wind projects. Morton County’s profile for renewables development is difficult, to say the least; Heatmap Pro’s modeling gives the county an opposition risk score of 92 because it’s a relatively affluent agricultural community with a proclivity for cultural conservatism – precisely the kind of bent that can be easily swayed by rhetoric from Trump and his appointees.
Morton County also has a proclivity for targeting advanced tech-focused industrial development. Not only have county officials instituted a moratorium on direct air capture facilities, they’ve also banned future data center and cryptocurrency mining projects.
Neighboring counties have also restricted some forms of wind energy infrastructure. McClean County to the north, for example, has instituted a mandatory wind turbine setback from the Missouri River, and Stark County to the west has a 2,000-foot property setback from homes and public buildings.
In other words, so goes Burgum, may go North Dakota? I suppose we’ll find out.
And more of the week’s top news about renewable energy conflicts.
1. Staten Island, New York – New York’s largest battery project, Swiftsure, is dead after fervent opposition from locals in what would’ve been its host community, Staten Island.
2. Barren County, Kentucky – Do you remember Wood Duck, the solar farm being fought by the National Park Service? Geenex, the solar developer, claims the Park Service has actually given it the all-clear.
3. Near Moss Landing, California – Two different communities near the now-infamous Moss Landing battery site are pressing for more restrictions on storage projects.
4. Navajo County, Arizona – If good news is what you’re seeking, this Arizona county just approved a large solar project, indicating this state still has sunny prospects for utility-scale development depending on where you go.
5. Gillespie County, Texas – Meanwhile out in Texas, this county is getting aggressive in its attempts to kill a battery storage project.
6. Clinton County, Iowa – This county just extended its moratorium on wind development until at least the end of the year as it drafts a restrictive ordinance.