Would just like to echo Karoshi's words here, these are NOT toys.
Standard training in awareness for All thunderflashes was to place an empty ammo can over one and stand well back. It DEFINATELY made all aware of the very REAL danger of having one of them land close to you and go off.
Speaking of certification, Lee can back me up on this, we saw some very interesting pictures of people who were treating these things as toys. Suffice to say that those who can still see are having a hard job holding things.
Pyro's are effective for displays and effect, but dont forget they are still explosives and as such should be treated with the utmost respect.