A fuel pod was a component found in starship propulsion systems.
When the deflectors aboard the USS Volga, carrying Kira Nerys, Julian Bashir, and Keiko O'Brien, became overwhelmed as they were traversing an asteroid field, in late 2372, and it was side-swiped by an asteroid, one of the runabout's fuel pods exploded. The explosion threw O'Brien against the bulkhead, nearly causing the death of her unborn fetus, Kirayoshi. (DS9: "Body Parts")