Linsey Marr, an environmental engineer, stood next to a pair of clear plastic boxes packed with tubes, nozzles and electronics, an odd-looking prototype that one day might serve to protect children in day care from airborne pathogens.

A nozzle filled the right-hand box with a faint silvery mist. A pump pulled some of that air into the left-hand box, where a sampler trapped floating particles and droplets. Soon, a digital screen bolted to the box turned red: “Detected! Dust mite allergen Der f 1.”

A protein shed by dust mites, Der f 1 can trigger asthma attacks when inhaled. Dr. Marr’s device had detected 843 picograms of Der f 1 per cubic meter. A single grain of salt is about 10 million times as heavy.

“Before this instrument, it would have taken us two days to figure out how much was in the air,” Dr. Marr said. “Now we’re doing it almost in real time.”

Dust mite allergens are not the only threats that Dr. Marr’s team aims to fish from the air. The technology, still evolving, can already sniff out influenza, the coronavirus and E. coli.

“We have 10 different things that we’re able to detect, and by the end of the program, there will be 25 different things,” she said.