As far as I know, many operators never witness this. I was invited to our facility's biannual test and accepted without understanding what I would observe. To be precise: the system is FM-200, not Halon, though the effect is similar. The test was scheduled for 02:00 local time. I understood this as consideration for minimal disruption. This was incorrect. The release is not a spray. It is a detonation of gas. The sound is extraordinary. The floor vibrates. Within four seconds, the room is opaque white and you cannot breathe without the emergency oxygen, which I had not been instructed to locate. I had propped the door open for ventilation while I waited. The gas escaped into the corridor, then through an open loading dock into the parking area. As far as I know, approximately 180 kg of FM-200 dissipated into atmosphere. Replacement cost: approximately €37,000. The environmental report, I am told, will be complex. The 02:00 timing, was to minimize witnesses. Not traffic. I understand now why veterans decline these invitations.
