Naar Directive was a brutal, yet efficient tactic to prevent infection of large ships by the Beast.
The directive states that in case of Beast infection, the plasma from the fusion drives is vented into the contaminated section. As a result, everyone in those sections dies nearly instantly. However, the plasma burns Beast matter as well, eliminating the infection before it could pose a threat.
It was created during the Battle of Coruc Farr when the Destroyer Naar-Tel was hit by an infection beam. Since then, it became standard procedure to defend against Beast infection. Despite it being fatal to everything in the endangered area, near-instant vaporization is still better than becoming part of the Beast neural network running through infected ships.