A French hospital has become the latest organization to announce promising developments in rapid COVID-19 testing—but don’t expect a speedy rollout of the technology it’s testing.

The Hospital La Croix-Rousse in Lyon is testing a machine in which patients breathe into a tube and get their coronavirus results within seconds. The trial has already been running for three months, and the hospital hopes to have the machine fully in use by the end of the year.

“It’s the same principle as a classic breathalyzer test,” Christian George, research chief at the hospital’s National Center of Scientific Research, told Reuters. “The machine will register the molecules in the exhaled air and then detects the traces of the sickness.”

However, the machine in question is not quite like your standard handheld breathalyzer.

For a start, the Vocus PTR-TOF—a cutting-edge mass spectrometer produced by Switzerland’s Tofwerk—weighs around 350 pounds and costs $460,000.

“These instruments are usually used in atmospheric science to measure clean air. That’s why they are so sensitive,” Tofwerk CEO Marc Gonin told Fortune on Thursday. Now the Vocus PTR-TOF is being tried out in a variety of other applications, ranging from the detection of oil-well emissions to the identification of fentanyl in lab samples.

“Anything that can be sniffed by a dog can be measured with our instruments,” said Gonin. “Dogs can sniff diseases and explosives. We are trying to do this.”

According to Gonin, one aim of the trial is to see what level of sensitivity is needed to get instant COVID-19 test results. The Lyon researchers are using the most high-end version of the machine, which has the greatest sensitivity. The cheapest version of the machine weighs around 110 lbs and costs $230,000.

So could the same kind of technology be made significantly smaller and cheaper for the purposes of a widespread rollout?

“It is possible to make it smaller, but it is not possible to make it smaller [while] keeping the same performance,” said Gonin. “These instruments are extremely performant right now. There is, of course, the hope that we don’t need all this full performance, and we can switch to a smaller, more compact, and less expensive instrument. It’s very difficult to say.”

Crucially, he added, “such an instrument is only useful if you can [get results] earlier than any other method.”

The breathalyzer method is certainly quicker than the other COVID-19 testing methods in use today—whether we’re talking about the extremely unpleasant nasal-swab test that is most widely deployed or the saliva-based tests that offer less discomfort but still take hours or even days for results to be returned (though that could soon be reduced to 30 minutes).

But some researchers, such as those at Virginia Tech who have devised a new droplet-testing system involving nanotechnology and laser beams, now claim to be able to get the test-to-results time down to mere minutes.