Signal flare

Ground flares are elongated tubes filled with a chemical that is ignited to produce light. The UNSC issues red-burning ground flares, sometimes referred to as a "fusee", for several tasks. They are most often used to illuminate weapons caches, mark paths for friendly forces, and to signal aircraft. They can also be used to mark locations for an artillery strike or as a crude flashlight of sorts.

The red light produced is most likely from strontium nitrate, potassium nitrate, potassium perchlorate, and a fuel such as sulfur, magnesium, aluminum, or polymeric resin. Ground flares can be seen in several location throughout Halo 3.