Tempreture drop script "spirit ontriggerstay" problems.

Hey ive been pushing my self to try new ideas with scripts with a mild knowledge of unity script. The script is for the room tempreture to drop on entering a spirt, then trigger an event. So far i have whats follows but the debug log dosnt confirm its working. Also is there a better way of writing this script maybe as part of a manager script?

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine; 
 
 public class roomTemp : MonoBehaviour {
 
     public bool TempDrop = false;
     public int roomtemp;
     public GameObject spirit;
     public Collider col; 
 
     // Use this for initialization
     void Start () 
 
     {
         roomtemp = 15;
         Debug.Log (roomtemp);
         if(TempDrop == true) 
         {
             roomtemp = -15;
         }
     }
 
     // Update is called once per frame
 
 
     void OnTriggerEnter (Collider col) {
 
       
         {
         if (col.tag == "spirit") 
         {
                 TempDrop = true;
         }
             Debug.Log (roomtemp);
         }
     }
 }