With my job, I do a lot of On Site job analyses for companies that are having a lot of occupational injuries (I am a Physical Therapist). I just recently spent several days at the Penn/Head tennis ball plant in Phoenix (really, I did). There is no "pressure" inserted into the balls that would cause them to explode. The balls are just glued together in big presses that look like muffin tins. As a matter of fact, the sound you hear when you open a can of tennis balls, that whoosh sound....it has absolutely nothing to do with the balls being fresh, it is actually negative pressure in the can so that when we open it it makes that noise, that's the only reason they do that, it's becuase we the consumer like that whoosh sound, we THINK that we are then getting fresh tennis balls. I assure you that there is no pressure or gas inside of a tennis ball.
------------------
Todd & ZEUS 4/5/00 Fawn male, cropped, docked, white toes and "goatee."