Plasma coolant

Plasma coolant was a substance used to regulate the operating temperature of a starship's warp core. Without it, the system could overheat or fail completely.

Plasma coolant was considered a biohazard and would react violently with organic matter, liquefying it on contact. The USS Enterprise (NCC-1701-E)'s warp core had two plasma coolant tanks. 

A coolant leak was known to either cause or be the precursor to a warp core breach. 

In 2374, one of USS Voyager's coolant injectors ruptured, causing a plasma coolant leak. 

Background
Coolant dangers aboard a starship have also been depicted in.

The loss of plasma coolant causing adverse effects to the warp core does not seem to apply to the USS Enterprise (NCC-1701-E). In, when Data breached the primary coolant tank in main engineering, it did not appear to have any adverse affect on the engines, even though the warp core was powered. It is possible that Starfleet engineered a solution to this problem by having two tanks so that in the event of the failure of one, not all the coolant would be lost. It can also be hypothesized that since the warp engines were not active during the "First Contact incident", the rupture of one of the two visible plasma coolant tanks was not sufficient to cause a thermal overload of the warp core reaction chamber.

Plasmakühlmittel