A leak occurs when something escapes from a structure designed to contain it.
Air leak
- (ENT: "Shuttlepod One")
Plasma leak
- A faked plasma leak. (ENT: "Stratagem")
- In 2368, a plasma leak aboard the USS Enterprise-D caused a warp core breach after a collision with the USS Bozeman. (TNG: "Cause and Effect")
- A Skrreean starship suffered a plasma leak in its engine core. 2370. (DS9: "Sanctuary")
- Deep Space 9's Lower Pylon One suffered a leak in 2370. (DS9: "Blood Oath")
- A leak in a plasma injector caused a runabout to cross over into the mirror universe. (DS9: "Crossover")
- Harry Kim was fixing a plasma leak on deck five when he began having a panic attack. (VOY: "Memorial")
- The IKS Rotarran suffered a plasma leak on deck five after the primary plasma injector was damaged in a Jem'Hadar attack. (DS9: "Sons and Daughters")
- (DS9: "Rejoined")
Coolant leak
- In 2153, a coolant leak was part of a simulated shuttle flight. (ENT: "Stratagem")
- Shuttlepod 2 leaked plasma coolant when its thrusters were damaged after it grazed a rock face. (ENT: "Strange New World")
- In 2266, the toxic fumes from a coolant leak in the phaser system killed USS Enterprise crewman Robert Tomlinson during an engagement with a Romulan Bird-of-Prey. (TOS: "Balance of Terror")
- A coolant leak was caused by collsion with a quantum filament. (TNG: "Disaster")
- A coolant leak occurred during an alternate timeline battle with Klingons. (TNG: "Yesterday's Enterprise")
- In 2371, a coolant leak caused by battle damage led to the warp core breach that destroyed the USS Enterprise for the final time. (Star Trek Generations)
Radiation leak
- In 2366, radiation that had leaked from Doctor Nel Apgars station in orbit of Tanuga IV threatened the USS Enterprise-D's antimatter pod. If the radiation had surged in or near them, it would have destroyed the ship. (TNG: "A Matter of Perspective")
- In 2367, the USS Enterprise-D discovered a small Talarian observation craft adrift in Sector 21947. The craft had developed a serious radiation leak in its propulsion system. (TNG: "Suddenly Human")
- In 2367, a massive radiation leak from a waste barge threatened to exterminate all life on Gamelan V. (TNG: "Final Mission")
- In 2370, a high-energy radiation leak was ignited by phaser fire, destroying a Skrreean ship. (DS9: "Sanctuary")
- A radiation leak from a loose plasma coil on an Antares-class transport prevented the beam-off of an injured Vedek Bareil Antos. {DS9: "Life Support")
- An antimatter radiation leak from Earth probe Friendship 1 caused radiation sickness to occur on a planet in the Delta Quadrant. (VOY: "Friendship One")
- Malon waste export vessels could jettison their Theta storage tanks if a radiation leak occured. (VOY: "Juggernaut")
Other leaks
- A small gas leak. (ENT: "Doctor's Orders")
- (ENT: "The Breach")
- A chlorinide leak. (TNG: "Ethics")
- A beer leak occured when the glass holding it was contaminated with invidium. (TNG: "Hollow Pursuits")
- A thorium leak. (DS9: "Crossover")
- Tamal became concerned about a neutrino leak in the port nacelle when Thomas Riker and the Maquis stole the USS Defiant. (DS9: "Defiant")
- (VOY: "Learning Curve")
- A fuel converter leaking veridium isotopes could cause a warp core breach. (VOY: "Drive")
- In 21st century Earth slang, to "take a leak" means to urinate. (DS9: "Past Tense, Part I"; Star Trek: First Contact)