Plasma vent

A plasma vent was a component of warp drive technology allowing excess plasma to be ejected harmlessly into space.

The secondary plasma vent on vessels had a triple redundant bypass meaning that the primary access junction was routed through the port transducer matrix. 

In 2152, a cloaked Romulan mine attached itself to the hull of just behind the secondary plasma vent. 

Later the same year, a Retellian freighter expelled a cloud of dilithium hydroxyls and ionized pyrosulfates into Enterprise's path, clogging the plasma vents and preventing the ship from engaging its warp drive. 

In late-2152, two Enolian patrol ships were disabled after Captain Jonathan Archer opened the plasma vents of the prison transport ship he was on and ignited the plasma cloud with weapons fire. 

On stardate 51932.4, while the USS Voyager was proceeding through a dense nebula cloud with the crew in stasis, Seven of Nine stated in her log entry that she would have to purge the auxiliary plasma vents in order for the ship to continue to operate effectively.