How should the back of the service tag be marked?

The back of the service tag is marked with the words "no listing mark" when the inspection or service does not meet the necessary standards for listing, indicating that the equipment is not in compliance with the applicable regulations or guidelines. This notation serves as a clear communication tool, informing anyone who reviews the service history that the extinguisher has either been found to be non-compliant or has not been verified against the required safety standards.

In contrast, marking the back with "completed service," the technician's signature, or the date of service reflects compliant conditions and good standing for fire safety equipment, which would not apply if the item is non-complaint. Therefore, "no listing mark" is critical for compliance issues and helps to track the status of the fire extinguisher accurately.