Burst disks are designed to vent air at extreme pressure thresholds to help protect us. There are many reasons a burst disk could let go, one may be a failed regulator. One time I had a burst disk on a 66 CF carbon fiber tank blow on me. Here is what happened in my case to cause the problem. I had some full tanks sitting in the back camper shell of a truck on the way to a hunting trip. It was summer and the day time temps were in the high 90’s. When we stopped for lunch the temperature in the camper shell started to climb. This resulted in the full CF tank to heat up. When the air in a high pressure tank increases so does the pressure inside the tank. When the pressure in the tank rose from 4500 psi to around 7500 psi the 7.5k burst disk gave way and the tank started to safely vent off all the air in the tank. Without the extra level of protection the burst disk offered the situation could of been much worse. Replacement burst disks are good to have on hand for situations like this.