ParticleSystem.CollisionModule.maxKillSpeed

Description

Kill particles whose speed goes above this threshold, after a collision.

Additional resources: ParticleSystem.collision.

using UnityEngine;
using System.Collections;

[RequireComponent(typeof(ParticleSystem))]
public class ExampleClass : MonoBehaviour
{
    private ParticleSystem ps;
    public float hSliderValue = 8.0F;

    void Start()
    {
        ps = GetComponent<ParticleSystem>();

        var collision = ps.collision;
        collision.enabled = true;
        collision.type = ParticleSystemCollisionType.World;
        collision.mode = ParticleSystemCollisionMode.Collision3D;

        var collider = GameObject.CreatePrimitive(PrimitiveType.Sphere);
        collider.transform.parent = ps.transform;
        collider.transform.localPosition = new Vector3(0.0f, 0.0f, 13.0f);
        collider.transform.localScale = new Vector3(20.0f, 20.0f, 20.0f);
    }

    void Update()
    {
        var collision = ps.collision;
        collision.maxKillSpeed = hSliderValue;
    }

    void OnGUI()
    {
        hSliderValue = GUI.HorizontalSlider(new Rect(25, 40, 100, 30), hSliderValue, 0.0F, 10.0F);
    }
}