OnTriggerStay is called almost all the frames for every Collider other that is touching the trigger.

This message is sent to the trigger and the collider that touches the trigger. Note that trigger events are only sent if one of the colliders also has a rigidbody attached.

Note: OnTriggerStay function is on the physics timer so it wont necessary run every frame.

	// Applies an upwards force to all rigidbodies that enter the trigger.
	function OnTriggerStay (other : Collider) {
		if (other.attachedRigidbody) {
			other.attachedRigidbody.AddForce(Vector3.up * 10);
		}
	}

using UnityEngine;
using System.Collections;

public class Example : MonoBehaviour {
    void OnTriggerStay(Collider other) {
        if (other.attachedRigidbody)
            other.attachedRigidbody.AddForce(Vector3.up * 10);
        
    }
}

import UnityEngine
import System.Collections

public class Example(MonoBehaviour):

	def OnTriggerStay(other as Collider) as void:
		if other.attachedRigidbody:
			other.attachedRigidbody.AddForce((Vector3.up * 10))