Victim Rescue and Recovery Test No. 2 From IFSTA Hazmat for First Responders 4th Edition Progress Indicator: Question 6 of 15 6.  Which of the following is not necessary to advance a fresh air base in single-level, room-and-pillar mines. Choices: construct a new air lock at the site of the new fresh air base repair damaged ventilation controls to the point where the new fresh base is located provide an opening for intake air provide an opening to the exhaust.  Return to the old fresh air base and remove that air lock and any bulkheads in parallel entries all of the above