I hesitate to call it “a” device because there are multiple devices.
I would support devices that use fuel cell technology. There are devices out there that use semiconductor technology, and the semiconductor technology tends to be a lot less.... It used to be, anyway; maybe it's improved. In years past, semiconductor technology was subject to fluctuations in accuracy because of the calibration of these devices, and a lack of keeping them calibrated.
These devices that we're familiar with, if used properly, will give you accurate and reliable results—at least, inasmuch as I know—as approved screening devices. I would expect it to be the same with the passive detection, but we have yet to test that.