Captain Ventralis informs you that Matriarch Benezia is in the hot labs. He gives you access to the area once you've dealt with the rachni during your initial conversation. Once you enter the hot labs after receiving access, you cannot leave without activating its purge function. Note: If you do this mission before dealing with Benezia then go back to the survivors, they will all attack you at the same time under the Matriarch's orders. If you dealt with Benezia first, then the elevator next to the Hot Labs one will be locked out.