Explosion Timeout

Hey can someone tell me how to end a explosion flame, my game has alot of enemy's and when they shoot there gernade launchers the Flame from the explosions stays forever which causes lag can anyone tell me how to make so the flame from the explosion dissapears 1-3 seconds after impact?

Can't you just use the autodestruct variable?

Give the particle emmitter a script that tells it to set onShot to true, after 3 seconds. This will make the emitter go for 3 seconds and then gradually dissappear in 1 or 2 seconds.