Final answer:
Cylinders exposed to high temperatures or damaged during a fire must be permanently removed from service to prevent potential future hazards.
Step-by-step explanation:
When cylinders are involved in a fire, certain safety protocols must be followed to ensure they are handled properly. According to standard safety regulations, any cylinders that have been exposed to high temperatures or structural damage during a fire must be permanently removed from service. This is to prevent possible future hazards, as the structural integrity of the cylinder may be compromised, making it unsafe for continued use. These cylinders include not only those that contain gases used in industrial and laboratory settings, such as oxygen, acetylene, or nitrogen, but also those in medical facilities, such as oxygen tanks. It is critical that these cylinders are not returned to service as they could fail and potentially cause harm or further incidents.