Instantiate keep on cloning my object - How can I stop it!?

I'm trying to make a destructible object by using 2 codes that I learned from a tutorial. http://gamedevelopment.tutsplus.com/tutorials/how-to-make-an-object-shatter-into-smaller-fragments-in-unity--gamedev-11795

At first, it was somewhat working. But after I added a few more codes of mine in it, it got messed up. It keeps on cloning and made my whole game lagging.

using UnityEngine; using System.Collections;

 public class Destroy : MonoBehaviour
 {
     public GameObject remains;
     private PlayerInteract securityCheck;
     public bool destroyed = false;
     // Use this for initialization
     void Start()
     {
         destroyed = false;
         securityCheck = GameObject.Find("Player").GetComponent<PlayerInteract>();
     }
 
     // Update is called once per frame
     void Update()
     {
         if (securityCheck.doorOpen == true)
         {
             StartCoroutine(BOMB());
             destroyed = true;
         }
     }
 
     IEnumerator BOMB()
     {
         yield return new WaitForSeconds(1);
         Instantiate(remains, transform.position, transform.rotation);
         Destroy(gameObject);    
     }
 }

This is the 2nd code. It did destroyed my original object but didn't do anything with the clones.

 public class SelfDestruct : MonoBehaviour {
     private Destroy destroy;
     public ParticleSystem explode;
     // Use this for initialization
     void Start () {
         destroy = GameObject.Find("Cube fragment").GetComponent<Destroy>();
     }
     
     // Update is called once per frame
     void LateUpdate () {
         if (destroy.destroyed == true)
         {
             ParticleBoom();
             StartCoroutine(Destroy());
             Destroy(explode);
         }
     }
 
     IEnumerator Destroy()
     {
         yield return new WaitForSeconds(2);
         Destroy(gameObject);
         Debug.Log("Bang Bang Bang");
     }
 
 
     void ParticleBoom()
     {
         explode = (ParticleSystem)Instantiate(explode, transform.position, Quaternion.identity);
     }
 }

And my explode particle system isn't working properly either, it keeps on cloning and exploding, so I had to destroy its "explode".