Here’s how to fix them — and what’s getting in the way.

For years, Alan, a designer in Vermont, had a persistent, hacking cough that kept him up at night, and every winter, a near-constant series of sore throats and colds. He visited his doctor’s office, got diagnosed with reflux, and took reams of antibiotics for suspected sinus infections. But the cough always came back, so intransigent it permanently hoarsened his voice.

One spring, his doctor hired him to design an addition to his home. Alan invited him to his office to review the plans. “He just walked in the door, took one whiff, and said, ‘Whoa, that’syour problem,” recalled Alan, who requested we only use his first name. 

The sharp air — a combination of off-gassing from an ammonia-based blueprint copier and fumes from two construction workshops that shared the building — was, to the doctor’s nose, immediately and unambiguously toxic. Later, a pulmonologist who looked at the insides of Alan’s lungs with a tiny camera said they looked like he’d survived a chemical fire. 

But Alan himself barely noticed the smell anymore. “It was like the frog that’s boiled,” he said. Major problems in our environments can go entirely unnoticed if they happen gradually enough.

Although he’s been out of his old office space for a few years now, Alan still has a cough. He gets sick less often these days, but will probably have to take inhaled steroids for the rest of his life. “The damage was done,” he said.

There’s a version of Alan’s story that’s playing out again and again, all over the US. Whether we notice it or not, the air we breathe indoors can make us sick. For most of us, it’s not an industrial printer that’s contaminating the air: It could be the pollution from our ovens and stoves or the chemicals off-gassed from everyday household cleaners, or it could be the respiratory diseases exhaled by others we share our spaces with. Our indoor air can become toxic without us realizing it — but indoor spaces aren’t always designed with this in mind.

The technology and the human knowledge necessary to improve indoor air exist. But despite decades’ worth of science linking dirty indoor air with threats to human health, the public has simply learned to tolerate poor indoor air quality and all the downstream problems that follow in its wake. We are the frog that’s boiled.

The people who design, maintain, and manage the air inside America’s buildings now have a chance to make things right. The Covid-19 pandemic, spread by an airborne pathogen, prompted demands for a paradigm shift in the way we think about air quality. Now more than ever, it’s clear what we have to gain from improving indoor air quality: Not only could doing so help mitigate the next pandemic, but it could also lead to other large-scale improvements in health and productivity — and even bring the US closer to its climate goals. And it could help build a more equitable society, as rural and low-income Americans are most vulnerable to the negative health effects of air quality and crumbling infrastructure.

At the same time, cost, environmental concerns, a lack of enforceable indoor air standards, and the slow-changing nature of culture are formidable obstacles to scaling up air quality improvements inside the US’s aging building stock.

The past few years have seen a surge of new science, new air filtration technologies, and new political will to do something about it, but these advances will only make a difference if policymakers create regulations to ensure progress reaches the people and places that need it. 

In its March announcement of a Clean Air in Buildings Challenge, the White House urged states, local governments, and schools to use any of the half-trillion dollars they got through the American Rescue Plan to improve buildings’ indoor air, signaling that the issue is increasingly one of national priority. But a challenge isn’t an imperative; there’s no law requiring buildings to participate. 

Can the US finally overcome the inertia that has put clean indoor air out of reach for so many Americans? A lot is still standing in the way. 

How the indoors got so stuffy

Humans have been using fresh air to cure and prevent disease for as long as we’ve understood diseases to be something other than punishment from the gods. But where we encounter clean, fresh air has changed with time and technology.

In the early 1900s, buildings were generally constructed of wood, stone, clay bricks, and other natural materials that generally did not emit airborne toxins — and they were drafty, often allowing outdoor air to circulate whether people wanted it or not. Over the course of the next century, the building blocks of modern construction changed: Plastics were the future, and new or renovated buildings began incorporating contemporary materials like synthetic carpets and glues, pressed wood products, and vinyl into their designs — and with them, a variety of toxic compounds they silently emitted.

Meanwhile, the global energy crisis of the 1970s incentivized architects and engineers to design buildings that were increasingly airtight — why pay money to heat a building just to see that heat escape out a crack around a window? That, in turn, required new approaches to controlling their interior climates. Mechanical systems for heating, ventilation, and air conditioning (HVAC) became more common, as did open-plan layouts to allow for better air circulation.

Every day, people entered sealed buildings held together with solvents, adhesives, particle board, drywall, and all of the chemicals that came with them. Reports of “office illness” crept into the media, and in the early 1980s, the World Health Organization coined the term “sick building syndrome” to describe the constellation of symptoms caused by the invisible byproducts of modern construction.

The structures intended to keep people safe were instead becoming threats to their health in a variety of ways. Bad lighting was causing headaches and eye irritation; noise and vibration were leading to nausea and dizziness. And all sorts of airborne contaminants were causing a host of respiratory illnesses.

Among the most insidious of those airborne pollutants are volatile organic compounds (VOCs) like formaldehyde and benzene, gaseous and sometimes odorless chemicals that were (and occasionally still are) found in everything from compressed wood to body lotion. Particulate matter — bits of residue thrown off from unvented heaters, candles, cigarettes, and other sources — was also a key offender. These pollutants can cause mild symptoms like eye and nose irritation but are also strongly associated with asthma, worsened respiratory and cardiovascular illness, low birth weight, and several types of cancer. And they were all over the buildings that were making so many people sick. 

It wasn’t just the buildings’ and furnishings’ byproducts making inhabitants ill. If people became sick in one of these sealed-up buildings, the airborne pathogens they spewed could linger, spreading respiratory infections. When HVAC systems didn’t adequately clean the air or the airflow in a building wasn’t carefully managed, disease-causing molds, bacteria, and viruses could spread not only from buildings to people, but from people to people. Under the right conditions, certain building features could intensify the transmission of disease.

Buildings have gotten better — but not better enough

The worst offenses against many of our senses are relatively easy to detect: Most people can tell when lighting is bad or when a building’s bowels groan too loudly. But our capacity for sensing bad air is less finely tuned.

We certainly can tell when the air is too hot or too cold for our liking. But we’re much less likely to notice the air we’re breathing has high levels of carbon dioxide — indicating we’re breathing a lot of other people’s expelled air — or contains dangerous VOCs. When we get headaches after a day in a stuffy conference room or a nagging cough that starts a few minutes after we walk into the building, how often do we wonder if the problem is in the air? 

Our sense of smell is only good for detecting indoor air quality on the really extreme end of bad, said Ian Cull, a Chicago-based environmental engineer who specializes in indoor air quality. We might notice the rancid or stale smell of mold, but there’s a lot we can’t detect. “We can probably, with our nose, tell the D minuses and the F’s,” he said, “but from an A plus to a C minus, you don’t really know.”

In the 1990s, a wave of lawsuits holding architects and engineers liable for health problems related to poorly built or maintained buildings led to massive overhauls of construction codes. The new codes created restrictions for the materials architects and engineers could use in buildings and HVAC systems. “Buildings were afraid of litigation,” said Sachin Anand, an engineer who leads a Chicago-based sustainable building firm. So most of them made meaningful changes that ultimately led to much healthier indoor climates all over the US. 

By the early 2000s, complaints of sick building syndrome — and concerns about indoor air quality more broadly — had faded from the public eye. 

Health problems related to bad indoor air still existed — it was just hard to prove in any individual’s case that their built environment, and not some other factor, led to a particular illness. Research accumulated linking indoor air pollution to worse cardiovascular disease; cognitive decline in older adults; higher rates of chronic respiratory diseases, lung infections, and cancers; and infectious diseases including measles, tuberculosis, chickenpox, influenza, and SARS. In schools, high levels of multiple pollutants and carbon dioxide were tied to lower academic and cognitive performance and worsened respiratory health for students — with the worst consequences accruing to children of color and low-income children.

Still, there were no national requirements to improve building designs that force hundreds of people to share the same air space. Huge numbers of students, office workers, nursing home residents, and apartment dwellers were stuck regularly breathing poor-quality air. It wasn’t clear exactly how many were breathing bad indoor air because there was no broadly accepted definition of “regularly” and “poor-quality.” (This is still true today.) And while people complained about how annoying and paradoxically antisocial designs like open-concept offices are, they rarely protested the health risks of these kinds of layouts. 

This was the state of things when Covid-19 arrived. The virus exploded, and almost instantly showed itself to be particularly good at infecting people in indoor spaces with poor ventilation and poor air filtration — like in many open offices, classrooms, and restaurants.

It took much longer than it should have for health authorities to publicly acknowledge that aerosols — tiny flecks of fluid, like those created when people cough or sneeze — could transmit SARS-CoV-2, the virus that causes Covid-19, through the air. But scientists were quicker to the draw, and the public’s awareness of the new dangers of sharing airspace changed overnight. 

“We’re in a place where people know that indoor air quality is important, but they’re just uncertain as to what to do,” said Cull.

Brett Singer, an environmental scientist and indoor air quality expert at the Lawrence Berkeley National Laboratory in Berkeley, California, agreed. 

“Covid was a big wake-up call,” he said. “Whether it’s going to be a sustained concern that’s going to allow us to make the kind of structural and cultural changes that we need is an open question.”

The three most important tools on the indoor air quality workbench

As the coronavirus turned lives and economies upside down, newly formed companies flooded the market hawking air filtration technologies. Some were evidence-based, but many, like air cleaners that emit the pollutant ozone, not so much.

So what’s a building operator to do? The tools available for managing indoor air quality generally fall into three categories, each with its own pros and cons. 

• Ventilation involves replacing a building’s stale air with fresh air, whether by opening doors or windows or by engineering an HVAC system to suck in air from outside. Cull said there are dose-response gains to increasing ventilation, meaning, “The more outdoor air you bring in, the better health benefits and productivity benefits you get,” he said.

On the flip side, ventilation is costly, especially during seasonal temperature extremes; it consumes a lot of energy — and dollars — to heat or cool a large volume of air. For that reason, cost-conscious building operators sometimes ventilate buildings less in the peak of winter or summer. 

• Air cleaning purifies the air by removing particulate matter — including viruses, molds, and bacteria — either systemwide through an HVAC system or by using standalone air cleaners in individual rooms. Those standalone cleaners are cheaper upfront than a full HVAC overhaul (which can run into the millions of dollars in a large building), and their filters can be more easily upgraded to catch smaller infectious particles.

However, filtration doesn’t remove volatile organic compounds from the air — that requires ventilation. And standalone units can be prohibitively noisy. Cull said that in schools, many of which spent millions of dollars on these units, teachers often kept them on the lowest setting “just for the acoustics,” greatly reducing their effectiveness.

Air cleaning can also involve treating air with ultraviolet radiation, which is an effective tactic for reducing the recirculation of disease-causing germs along with air in an HVAC system. However, UV systems can be expensive, and they require careful attention to ensure they’re used safely. 

• Source control, finally, involves removing or avoiding things that emit chemicals or other contaminants — like certain building materials or furnishings, noxious cleaners, and cigarettes. Appliances that combust gas, like gas stoves, are often the worst offenders in the modern-day home.

Source control is the most cost-effective strategy overall, said Cull. However, it still requires profit-motivated contractors to choose building materials that don’t emit volatile organic compounds, or to switch a building’s utilities from gas to electric — a move that brings big indoor air quality benefits. All those solutions can be costly or challenging. 

It takes a building-by-building adjustment in each of these categories to achieve healthier buildings while minimizing financial costs and climate impacts. 

But making that adjustment is not straightforward.

One of the biggest challenges comes before any of these tools are deployed. In the US, the EPA doesn’t regulate indoor air, and there’s no federal standard for indoor air quality. That means there’s no minimum for building managers to strive for, and no way for inhabitants to know what’s in the air they’re breathing.

Still, there is guidance telling engineers and architects how to design buildings with air quality in mind.

The American Society of Heating, Refrigerating and Air-Conditioning Engineers — ASHRAE, a professional association whose guidance outlines minimum standards for acceptable indoor air quality — updated its recommendations after the pandemic began.

ASHRAE’s standards include minimum ventilation rates that a building’s HVAC system should have, and measures that should be taken to prevent contaminants from entering inhabitants’ air supply. But it doesn’t include a requirement to check whether any of those controls are working. 

Broadly speaking, there’s still no standard for assessing indoor air quality as a whole — only individual measurements quantifying its components. Effective sensors to detect carbon dioxide, carbon monoxide, and particulate matter are available on the retail market, but there’s no widely approved composite score that communicates indoor air quality the way the Air Quality Index does for outdoor air quality. No simple parameter captures the safety of a building’s air in a way that’s meaningful to the public; no unambiguous reporting metric exists to facilitate accountability. 

Without this, building owners have little incentive to improve bad air, said Cull. 

He imagines something akin to the health department score many restaurants have to post up front: “The restaurant owner doesn’t want to have that sign, but it’s a requirement to post that they got a B minus for hygiene and cleanliness,” he said. Perhaps building operators should be doing the same for the air they offer inside. 

What’s keeping us from having clean indoor air in every US building right now?

Besides the lack of meaningful standards or regulation, the upfront cost of improving indoor air quality is one of the biggest obstacles to achieving it.

At a minimum, gold-standard building designs involve electric utilities rather than gas, and an HVAC system powered to drive a full fresh air exchange of the building’s air four to six times an hour. They also clean the air using high-efficiency filters. Achieving that standard is an expensive project, usually in the range of several million dollars for a high-occupancy building.

Building operators with large budgets and a lot of motivation can and do spend that kind of money to make the changes they need to make.

Steve Hanon leads campus operations at Avenues, a private K-12 school with multiple international campuses. He spared no expense to ensure that the HVAC systems in the school’s newest campuses are being built to the highest standard. He says what made that possible was that the school’s leadership has prioritized it. 

Making things easier: “We’re a premium school,” said Hanon; annual tuition is nearly $63,000.

American public schools are in a very different position. In schools with disproportionately high numbers of low-income students, resources for making capital improvements are often scarce, and facilities — including HVAC units — are disproportionately out of date. In a recent workshop, Hannah Carter, who manages school air quality projects at the US Green Building Council, said these schools often lack adequate facilities staff to keep up with needed changes, and may be less likely to get guidance on improving their air quality from federal sources. “It’s definitely an equity issue,” she said.

Public schools’ facility budgets are usually fixed, and except in the richest districts, relatively modest, making it prohibitively expensive to achieve the gold standard. And while federal grants like those available through the American Rescue Plan and the CARES Act are meant to make premium upgrades attainable, they don’t always work the way they’re supposed to.

Consider the case of the Milford School District in southern New Hampshire. Buildings and grounds director Bill Cooper knew that one of the highest-impact changes he could make would be to replace the five aging HVAC units that served the high school.

When Cooper heard federal dollars were available for school districts to make improvements aimed at mitigating Covid-19 transmission, he jumped at the opportunity to get funding. But he quickly found there were enormous obstacles to clear: He had to get a detailed set of plans approved by the state fire marshal’s office, which required bringing in an engineer to make each unit’s drawings and plans to an exhaustive level of detail. “That’s a lot of work,” said Cooper. 

With a small staff already stretched thin, he demurred, instead opting to make do with a pallet of box fans — what amounts to a temporary and seasonally imperfect fix. 

He’ll replace the HVAC units somewhere down the line on the district’s own dime, when red tape is less of an issue. “You have to jump through all these hoops,” Cooper said. 

Although the price tag may prevent many building operators from making initial investments in permanent and effective air quality solutions, Joseph Allen, an environmental health expert who founded the Healthy Buildings program at the Harvard T.H. Chan School of Public Health, argues that the payoffs outweigh these investments by several orders of magnitude. In a 2015 publication modeling costs and benefits of doubling office buildings’ ventilation rates, Allen and his co-authors found businesses had a lot to gain from relatively small investments in workers’ air quality.

The benefits: lower rates of absenteeism and sick leave, lower health care costs (as a result of lower incidence of health care use due to influenza, pneumonia, and other respiratory infections), and higher productivity due to better cognitive performance and productivity. “When we do the economic analysis,” said Allen, “we show that the cost is on the order of tens of dollars per person per year — against benefits of six to seven thousand dollars per person per year.”

But there’s a wrong-pockets problem here: Most of the savings Allen points to don’t end up accruing to the building owner, who ultimately bears the cost for improving the building. While investments in a building’s engineering can lead to a higher resale or rental value — gains that do end up in the owner’s pockets — that profit can take a long time to be realized, and most building operators want to see a return on their investment in three to five years, said Cooper, the school facilities director.

It’s not just the price tag that’s holding back change 

Many of the interventions that lead to cleaner indoor air consume additional energy — often, a lot of additional energy. And in the US, coal still supplies about a fifth of the nation’s electricity. It’s not ideal to create more outdoor air pollution in pursuit of cleaner indoor air. 

Fortunately, it’s entirely possible to have healthy buildings that use very little energy, Singer, the environmental scientist, said. When it comes to indoor air quality, climate and health priorities “are absolutely compatible, but attention needs to be paid to both in order to accomplish that,” he said.

Among the clean air building strategies that reduce climate impacts are HVAC tune-ups to improve energy efficiency, and novel technologies like energy recovery ventilation, which uses the warmth or chill of exhausted stale air to heat or cool fresh air being brought into a system.

Older strategies — perhaps the oldest ones — also work: opening windows is an incredibly cheap, effective, and climate-neutral way of increasing ventilation. 

But these strategies only help if they’re used. Anand, the sustainable building engineer, said because windows that don’t open and close are cheaper than those that do, many high-occupancy buildings have inoperable windows.

That trend highlights one of the biggest barriers to industry-wide change: culture. Although plenty of strategies exist to overcome cost and climate concerns in the service of healthier indoor air, getting decision-makers to choose to construct and run buildings differently means asking many people to realign their priorities, with the impediments often clearer than the incentives. 

When Tom White, who works for an affordable housing nonprofit in the Bay Area, switched one apartment building’s utilities from gas to electric, he encountered resistance from all sides. White said the choice rankled both the workers putting in the new electric conduits and the pipefitters who lost out on work setting up the building for gas. “It’s like, ‘Why would we want to change when we have all of this energy just sitting in the pipe right there?” he said.

If a change like this is so challenging to make even in California, with its climate-forward political culture and many green building incentives, how much harder is it to make in states where fossil fuels run the table?

Everyday people need to be empowered to demand cleaner indoor air 

The pandemic has made Americans perhaps more aware than ever of the links between clean indoor air and their health.

But what they still lack is leverage. Even after a global pandemic made filtration and ventilation household words; even after the business case for healthier buildings was made clear in books and the press; even with mountains of data on one side, there is little regulatory recourse people can use to back up their demands for better indoor air. 

We shouldn’t need carrots and sticks to make our workplaces, schools, residences, nursing homes, and places of worship safe, and to engineer them to better protect us from common pollutants or the next pandemic. Our health should be enough of an incentive. But for indoor air quality to become a business priority in the US, we’re going to need something with more teeth. 

People need a clear path for demanding better when buildings fail them. They deserve transparent standards for indoor air, with metrics they can easily understand and use to make their own decisions. And they require policymakers to provide enough support — and consequences — for building owners to ensure they meet those standards.

“The cost of fixing that HVAC system to work properly, to provide good ventilation and filtration,” said Singer, is not the critical barrier. “The key barrier is not the cost. The barrier is the knowledge, the infrastructure, the culture.”