How to restart particles?

I need to make an object in a collision with another object appeared once the particles, and when they were new clashes did not appear. I decided that this can be achieved in this way. What do you suggest? ("trigger once" certainly does not help)

Example capx

Make sure your particles "Type" property is set to "One-Shot".

You did not understand me, I need to particles worked only once in a collision with an object, but not every time.

explain with an example. I need to do to effect checkpoint. When a character goes through it should work "fireworks". But it should not be triggered every time a character goes through it.

Example capx

thanks)