The heat producing glands of Scarrans are organs located in their upper chests. These glands help regulate the temperatures of their bodies, but also are directly responsible for the heat projection ability latent in all Scarrans. The gland produces enough heat to keep a Scarran alive and functional in even frigid environments but not enough for them to use their heat projection ability in such places.
A Scarran can survive having this gland remove, as was often done to Scarran prisoners of the Peacekeepers prior to the Peacekeeper Reformation. This not only prevents the Scarran from using their heat projection ability, but also physically weakens them. Without this gland, a Scarran is unable to survive in cold temperatures.
Heat producing glands are mentioned in Farscape.