One cool day in Eugene, Ore., James Meadow, in a tank top and shorts, climbed inside a sealed, sterilized chamber—a former refrigeration unit affectionately called the “pickle box.” The postdoctoral researcher at the University of Oregon's Biology and the Built Environment Center sat there for four hours, with no bathroom breaks, as 12 air filters collected the microorganisms emanating from his body.

“How much are humans giving off just sitting at the desk?” Meadow asks. He and his colleagues aim to find out.

The Oregon researchers keep tabs on what fills the air so they can design buildings that efficiently combine ventilation and filtration to surround occupants with the healthiest air possible. “If we're going to be constantly surrounded by bacteria,” Meadow says, “we may eventually get to a point where we can manage the indoor ecosystem the same way that we manage national parks.”

Preliminary data from the pickle box show that the assays can detect the presence of a single human and are beginning to pick out individual differences. For now, Meadow says, the built environment is uncharted ecological territory: “We know more about the bacteria that you find in deep ocean vents, or in the troposphere, or in rocks in Antarctica.”