Step 1 -	Measure the tube minimum anode voltage.
Step 2a -	Place the subject tube into a glass chamber, fill with hydrogen gas up to 760 mmHg.
Step 2b -	Apply 100°C heat at the chamber (by means of boiling water) for 72 hours.
Step 3 -	Measure the minimum anode voltage again.

1. Minimum anode voltage: Increase must be < 10% of initial value.