Which type of extinguishers requires a hydrostatic test every 12 years?

The requirement for hydrostatic testing every 12 years applies specifically to dry chemical extinguishers that have mild steel shells. This testing is crucial for ensuring the safety and reliability of these extinguishers, as it verifies that the pressure vessels are still structurally sound and safe to use.

Hydrostatic testing involves filling the extinguisher with water and subjecting it to high pressure, which allows any weaknesses or flaws in the materials to be detected. Since dry chemical extinguishers made with mild steel are more susceptible to corrosion and degradation over time compared to those made from other materials, this regular testing is essential to maintain their integrity.

In contrast, other types of extinguishers mentioned do not share this specific requirement or frequency. For example, CO2 extinguishers may require testing on a different schedule, and water mist or wet chemical extinguishers have their own distinct inspection and maintenance protocols that differ from those of mild steel dry chemical models. This highlights the importance of knowing the specific testing requirements for different types of extinguishers to ensure compliance with safety regulations and effective fire protection measures.