Which extinguisher type does not require weight to be marked?

The correct choice regarding extinguisher types that do not require weight to be marked pertains to pump tank calcium chloride based antifreeze extinguishers. These extinguishers operate differently from traditional portable fire extinguishers for several reasons.

Pump tank extinguishers, such as those that utilize calcium chloride antifreeze, are often larger and are designed to be operated manually with the aid of a pump. They typically contain water mixed with antifreeze to prevent freezing in cold conditions and may not be subject to the same regulations as smaller portable extinguishers. Due to their design as equipment that is not easily portable and their operational mechanism, weight marking is generally not applicable.

In contrast, dry powder extinguishers, CO2 extinguishers, and pump tank water extinguishers must have their weight marked for safety, maintenance, and compliance reasons. This marking allows users to know the amount of extinguishing agent available and ensures proper inspection and service can be conducted throughout the extinguisher’s service life. This requirement ensures that users are aware of the extinguisher's capabilities and that it is sufficient for extinguishing fires effectively.