The glass is about 3/4" thick. During the manufacture of the tube various tests are done to insure it meats UL requirements. These tests are not done on evert tube, just a sampling.
- first off the tube is positioned in a jig so that it is upright, it has a 7 Joule impact test. what this meams is a solid metal object shaped like a bulllet weighing 7 pounds is suspended on a rope like a pendulum, pulled back in a 7 foot arc and then let go so that it hits the center of the tube.... it cannot break or it fails.
- next the glass is frozen with nitrogen and the glass is scribed, the test is repeated and this time it will break, the glass cannot fall outside a line that is about 5 feet form the tube.
Bottom line your tube is probably safe, if it had chips around the "Frit seal" ( this is the white/grey seal that joins the faceplate to the tube) then it is a different story.
Hope this helps
Rick