How accurate does a torque wrench have to be?

I used to calibrate them for the USAF. Most were +/- 3% but some were more like the real low inch pound screwdrivers. They had to be temperature stabilized for 24 hrs at 70F and no more than 20% HUMIDITY before calibration. If I remember right they were calibrated at 10, 50 and 75% of their scale and also the highest setting. Before USE THAY HAD TO BE BROKEN 3 TIMES AT THE TORQUE THEY WERE GOING TO BE USED AT! I always thought that was kind of bull, because you took it out of the shop to the flightline and it could be 0 F out there or 130f and 80% humidity and what happened to the calibration if it is out of the testing conditions? If it was dropped they had to be re calibrated. Hope it helped and not confused you.