What does the 12-year hydro schedule require for maintenance of fire extinguishers?

The 12-year hydro schedule specifies that fire extinguishers using dry chemical and halogenated agents must undergo hydrostatic testing every 6 years. This testing is crucial to ensure that the integrity and reliability of the extinguisher remain intact over time. Hydrostatic testing involves filling the extinguisher with water or another hydraulic fluid and pressurizing it to check for leaks, deteriorations, or weaknesses in the cylinder that could compromise its functionality during a fire emergency.

This maintenance procedure is necessary as dry chemical agents and halogenated agents can have specific pressures and contain materials that could degrade or react unpredictably if the extinguisher is not properly maintained. Conducting hydrostatic testing at the prescribed intervals is an industry standard aimed at ensuring that fire extinguishers are in optimal condition, promoting safety and compliance with fire codes.

The other options pertain to different maintenance intervals and practices that do not align with the established hydrostatic testing requirements. Therefore, the correct choice reflects the necessary adherence to safety standards related to specific types of fire extinguishing agents.