Is hydrostatic pressure testing (HRT) mandatory for CO2 cylinders?

Yes, it is legally mandatory. Carbon Dioxide (CO2) extinguishers are high-pressure cylinders stored at pressures exceeding 50-60 bar. According to Gas Cylinder Rules (under the Chief Controller of Explosives - PESO) and IS 2190 guidelines, CO2 cylinders must undergo hydrostatic stretch testing every 3 years. The cylinder is pressurized to its test limit (250 kg/cm²) to ensure there are no structural fatigue cracks or thinning of the metal walls.