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’s your 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.

here’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.

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