Thermographic cameras detect radiation in the infrared range of the electromagnetic spectrum (roughly 9,000–14,000 nanometers or 9–14 µm) and produce images of that radiation, called thermograms. [wikipedia]
"Radiation" has (M)ultiple meanings/uses, and not all radiation is bad. Non-ionizing radiation — radio waves, visible light, microwaves, etc. — is generally harmless
