Coronavirus infections might soon be flagged with a puff of exhaled breath, after the Food and Drug Administration authorized the first breath-based Covid-19 test in the United States on Thursday.

The emergency use authorization of the InspectIR Covid-19 Breathalyzer is a meaningful milestone in the yearslong quest to develop more breath-based diagnostics, as well as innovative new tests for Covid, experts said. And it is likely to be the first of many similar breath-based Covid tests, experts said.

“I think this is a really exciting development for the entire field of breath analysis,” said Cristina Davis, the associate vice chancellor of Interdisciplinary Research and Strategic Initiatives at the University of California, Davis, who has been developing her own coronavirus test. “This is a huge step forward.”

But breath tests still pose real-world challenges, and this particular device has several practical limitations, scientists said. The machine required to conduct the tests is large — about the size of a carry-on suitcase — and can only be used by trained operators supervised by health care professionals.

And many devices would be needed for wide-scale screening, given that each machine can process only about 20 samples an hour, according to InspectIR Systems, a small, five-person company based in Frisco, Texas.

The company cited high accuracy rates for its tests, but some experts said they wanted to examine the data underlying its application to the F.D.A. before endorsing this test method.

In addition, many health care settings and mobile test sites where the devices may be used have already adopted other kinds of rapid tests, which are now widely available. InspectIR’s officials said that final pricing plans had not yet been set.

It could take 10 to 12 weeks for the first devices to hit the market, John Redmond, a co-founder of InspectIR Systems, said on Friday. The company said it planned to produce about 100 devices a week, according to the F.D.A., but it was not immediately clear when production would reach that level.

“We’ve been thinking about these types of tests for the entire pandemic, and we were kind of waiting for the first one” to be authorized, said Dr. Wilbur Lam, a pediatric hematologist and bioengineer at Emory University and the Georgia Institute of Technology and an expert on Covid tests.

“The devil is in the details to really determine how useful this thing will be,” he said.

Many diseases cause physiological changes that alter the compounds we exhale, and there has long been interest in developing breath tests for a wide range of illnesses, from lung cancer to liver disease.

When the pandemic began, numerous research teams began trying to identify unique chemical patterns in the breath of Covid patients, and many scientists and companies have been developing breath-based coronavirus tests, which could be used to rapidly and noninvasively screen large groups of people for the virus.

Some Covid breath tests have already been tested in pilot programs or authorized for use in other countries, but the InspectIR Breathalyzer would be the first to hit the market in the United States.

To use the device, patients blow into a cardboard straw attached to a chemical analyzer. “It’s a chemistry lab in a box,” Mr. Redmond said. The machine then analyzes the levels of five volatile organic compounds, or V.O.C.s, that together make up a “breath print” of Covid, Mr. Redmond said. (InspectIR said it could not disclose what the five compounds are.) Results are delivered within three minutes, the company said.

“That’s really fast and pretty impressive,” said Nathaniel Hafer, a molecular biologist and testing expert at UMass Chan Medical School.

Expanding the types of samples that can be used to detect the virus is “really valuable,” he added. “Not everybody can provide a nasal sample very easily.”

In a company-sponsored study of 2,409 asymptomatic people, the breathalyzer had a sensitivity of 91 percent, meaning that of the people who tested positive for the virus on a P.C.R. test, the device flagged 91 percent of them as presumptive positives, according to documents released by the F.D.A. It had a specificity of 99 percent, meaning it did not detect any signs of the virus in 99 percent of those who received a negative result from a P.C.R. test.

Susan Butler-Wu, a clinical microbiologist at the Keck School of Medicine of the University of Southern California, said that she wanted to see more independent data on the device’s performance and more details on precisely what compounds it was detecting.

“The use of V.O.C.s is not well developed for the diagnosis of infection,” she said. “I would not feel comfortable using it for diagnosing patients without getting some more real-world data.”

Certain foods and substances can throw off breath tests, scientists noted. And the instructions for the InspectIR Breathalyzer specify that people should not eat, drink or use any tobacco products in the 15 minutes before taking the test. Those who test positive should also have the result confirmed with a P.C.R. or other similar test, the company says.

Indeed, the most promising way to use breath tests is as a quick screening tool — a more accurate version of not-very-reliable temperature screens that became common during the pandemic, Dr. Lam said. “They don’t really give you a diagnosis,” he said, referring to breath tests. “They give you a biochemical pattern that is consistent with the disease.”

InspectIR hopes to lease the analyzers to other businesses, including health care facilities and companies that run mobile or pop-up testing sites. They could be used to test travelers at airports or workers in an office building, the co-founders said, adding that there has already been interest from professional sports leagues and companies in the travel industry.

“Anywhere that they’re doing a nasal swab more than once a day, we’re a great fit,” said Tim Wing, a co-founder of the company.

The device’s pricing has not yet been finalized, but the co-founders said on Friday that they hope to be able to offer licenses or subscriptions that translate to a cost of about $10 to $12 per test.

“Yesterday was a huge domino for us,” Mr. Wing said on Friday, the day after the device was authorized. “Not all this stuff is ready to go, is defined yet.”

The company said that it had raised $2.7 million to date and that Pfeiffer Vacuum would be its initial manufacturing partner.