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Memory Alpha

Release of plasma coolant

A schematic of the plasma coolant tanks aboard the Enterprise-E

Plasma coolant or reactor coolant was a gaseous substance used in the operation of a starship's warp core. It was denser than air and would displace it without mixing. Plasma coolant was considered a biohazard as it liquefied organic matter on contact. (Star Trek: First Contact)

A coolant leak often preceded a warp core breach. (TNG: "Yesterday's Enterprise"; Star Trek Generations)

In 2151, a shuttlepod from Enterprise began leaking plasma coolant from a damaged thruster while landing on Archer IV. (ENT: "Strange New World") Later that year, Lieutenant Malcolm Reed caught the common cold from opening a case of plasma coolant. (ENT: "Sleeping Dogs") Weeks later, Enterprise supplied a thousand liters of plasma coolant to the Vahklas. (ENT: "Fusion")

An Arin'Sen transport encountered by Enterprise in 2152 was venting reactor coolant from their port engine. (ENT: "Judgment")

In 2153, Captain Jonathan Archer faked a reactor coolant leak during an attempt to deceive Degra. (ENT: "Stratagem")

The Borg Queen dissolves in the plasma coolant

The USS Enterprise-E had two plasma coolant tanks on either side of the warp core. In 2063, Lieutenant Commander Data ruptured one of the tanks to destroy the Borg Queen. (Star Trek: First Contact)

In 2374, one of USS Voyager's coolant injectors ruptured, causing a plasma coolant leak. (VOY: "Day of Honor")

Shortly before its destruction by the Breen, the USS Defiant experienced eight EPS ruptures venting plasma coolant (DS9: "The Changing Face of Evil")

Coolant dangers aboard a starship were also depicted in TOS: "Balance of Terror".