Which type of extinguishers do not require verification of a service collar installed?

Cylinder-operated extinguishers are designed in a way that they do not require the same level of verification for a service collar as other types. A service collar is often an indicator that an extinguisher has been checked or serviced, but cylinder-operated extinguishers utilize a different mechanism and operational design.

In general, stored pressure extinguishers and portable extinguishers often require regular inspections, including checking that the service collar is intact and has not been tampered with since it provides assurance about the extinguisher's maintenance history. Class D extinguishers, which are specifically used for combustible metals, also follow specialized servicing protocols, including the need for verification of service collars to ensure they are functioning correctly.

By understanding the specific maintenance and operational requirements for different types of extinguishers, it's clear why cylinder-operated extinguishers are treated differently in this context.