With its five wall-length windows, Nick Crandall’s restaurant, Railroad Pub & Pizza, can bring in a lot of outside air. In late December, though, Washington state regulators said the restaurant could not qualify as “outdoor” dining, and would have to close because of heightened coronavirus restrictions.

So Crandall went to Facebook to protest, giving a video tour of the Burlington, Wash., pub and its vast, garage-door-style windows. “I’m just kind of curious on what the science is for outdoor dining, how much airflow you need to do,” he said. He took aim at the state’s Democratic governor, Jay Inslee, suggesting he use “common sense.” The video was viewed over 73,000 times.

It may sound like yet another politicized, Trump-era battle over coronavirus restrictions — yet this one ended in something that looks less like polarization and more like compromise. After Crandall and others complained and took to the media, state regulators introduced a new policy, which appears to be one of the first of its kind, allowing certain restaurants to count as “open air” dining even if they have four walls. In a new pandemic trend, these establishments can open up large windows or doors and actively measure levels of carbon dioxide, the gas we all exhale when breathing, as a key indicator of how much fresh air is circulating….

The impetus for measuring carbon dioxide is simple: An increasingly powerful body of evidence suggests the coronavirus is airborne, capable of traveling distances well beyond six feet in tiny aerosols released when infected people talk, shout, sing or just breathe. But there’s currently no sensor that can monitor, in real time, whether these infectious aerosols are floating around us when we’re indoors….