A much safer way of releasing the vacuum from a CRT is to break the vacuum seal, located within the locator key on the CRT base; that or knock the neck off. I knew kids in my old neighborhood near Cleveland who would throw rocks at the screens of discarded TVs on trash collection day, and I was amazed most of the kids escaped without being injured badly by flying glass when the tube imploded.
All CRTs, after all, are under tremendous vacuum pressure; listen one time when the vacuum seal breaks and note how loud the initial hissing sound is when air first enters the tube.