Fire Extinguishers Hydro Test is a safety testing process carried out to ensure the strength, durability, and reliability of fire extinguisher cylinders. In this test, the cylinder is filled with water and subjected to high pressure to check for any leaks, cracks, or weaknesses. Hydro testing is generally required every 3 to 5 years as per safety standards. It helps maintain compliance, extends the life of extinguishers, and ensures they will perform effectively during an emergency.