The fire suit and undergarments are what keeps you alive long enough to be extracted in the event of a fire. They are literally rated in terms of how long they

The fire suit and undergarments are what keeps you alive long enough to be extracted in the event of a fire. They are literally rated in terms of how long they protect you commonly listed as the "Time to 2nd Degree Burn" specification which is arrived at by taking the TPP rating per the SFI spec and halving it.