* Thermal sources: Any object with a temperature above absolute zero emits infrared radiation. The hotter the object, the more infrared radiation it emits. This is why you can feel the warmth of a fire or the sun on your skin.

* Electrical sources: Certain electrical devices, such as light bulbs and heaters, also emit infrared radiation.

* Chemical sources: Some chemical reactions, such as combustion, also produce infrared radiation.

* Natural sources: The sun is the most powerful natural source of infrared radiation. Other natural sources include stars, planets, and comets.