Why is there a requirement to guarantee it safe? I don't believe that requirement exists for tasers, for example, which are just considered less lethal. Same for rubber bullets.
If you're selling it as a nonlethal weapon, you should somehow make certain it's not going to kill except by freak accident, and cannot be used to kill deliberately.
Also, consider the safely of the police officer.
I have bad news about what is considered non lethal. They sell non lethal tank rounds, for instance.
These systems are called less than lethal.
Just "less lethal" is the current industry term, since it's acknowledged that these weapons are still capable of killing.