Turn Invisable Collider off and on

Im wanting to turn an invisable cylender colder I have place off and on. and I also need to toggle my particle emiter off and on for fire I have never called the off and on swich befor so I was hoping some one could provide me some help.

Unity makes it really easy to turn a component on and off. Most components have a property enabled that turns them active/inactive.

 function Start () {
       InvokeRepeating("FlipCollider" , 3 , 3);
       //Call every 3 seconds.
 function FlipColider () {
       collider.enabled = !collider.enabled;
       //flips the current value.  Makes it the opposite of what it currently is.
       //Most components either have an enabled or active(obsolete) property.

       particleSystem.enableEmmission = !particleSystem.enableEmmission;
       //The new Shuriken system has a slightly different name for enabled though.