Short answers, pulled from the story.
Thermography, also called infrared thermography or thermal imaging, is a technique in which a thermal camera detects infrared radiation emitted from the surface of objects to produce a visible temperature map called a thermogram. The camera integrates emitted, transmitted, and reflected radiation to estimate surface temperatures. Most thermal cameras operate in the long-wave infrared range of 7-14 micrometres.
The first infrared-sensitive electronic television camera was invented in 1929 by Hungarian physicist Kalman Tihanyi for anti-aircraft defense in Britain. The first American thermographic camera, an infrared line scanner, was developed by the US military and Texas Instruments in 1947 and took one hour to produce a single image. The first commercial thermal imaging camera was sold in 1965 for high voltage power line inspections.
Emissivity is a material's ability to emit thermal radiation, expressed as a coefficient from 0 to 1. Silver has a very low emissivity of 0.02, while asphalt has a high emissivity of 0.98. If a thermographer does not set the correct emissivity for the object being measured, the camera will underestimate or overestimate the object's actual temperature.
Thermography is used by firefighters to see through smoke and find people, by power line technicians to detect overheating joints before failure, and by building inspectors to locate heat leaks and moisture. Medical uses include fever screening, peripheral vascular disease screening, and thyroid gland assessment. The military and law enforcement use it for night surveillance and target detection.
Cooled thermal cameras use detectors chilled to cryogenic temperatures, typically between 60 and 100 Kelvin, producing superior image quality but at high cost and with energy-intensive cooling systems. Uncooled cameras operate at or near ambient temperature using microbolometer or ferroelectric sensors, making them smaller and cheaper, though with lower resolution and sensitivity.
Government and airport personnel used thermography to screen for suspected swine flu cases during the 2009 pandemic. The technique allowed for non-contact detection of fever in travelers passing through airports and border crossings.