Rad Immunity
Rad Immunity is a core resource shown in the status bar. It is spent when performing many scavenging and gathering jobs, representing your protection while working in irradiated areas.
A job's requirements show its exact Rad Immunity cost. You must have enough available to begin the job, and the cost is deducted when the attempt starts.
Recovery
Rad Immunity regenerates by 1 point every 5 minutes until it reaches your current maximum. Consumable items can restore additional Rad Immunity; open an item's details to see the amount restored and any cooldown or temporary effect.
Maximum Rad Immunity
Your base maximum is 10. The Immunity perk increases the maximum by 5 points per level, up to 50 additional points at level 10. Membership and temporary effects can increase it further.
Increasing the maximum lets you save more Rad Immunity between sessions, but does not change the normal regeneration rate.
Cost reductions
Some bonuses reduce the Rad Immunity cost of jobs associated with a particular skill, such as Fishing, Mining, Woodcutting or Scavenging. Applicable reductions are combined, then the final cost is rounded up to a whole point and cannot fall below 1.
Several Trophies provide these skill-specific reductions. A fractional bonus may not change a job's displayed cost by itself because the final amount is rounded up, but multiple bonuses can combine into a full-point reduction.