The chemicals in fire extinguishers are under high pressure, which can cause damage to the device over time. Hydrostatic testing must be done to guarantee that the fire extinguisher is still in good working condition. A professional will inspect the hose, shell, and nozzle for flaws that could cause it to fail. During hydrostatic testing, we empty the fire extinguisher and fill it with dyed water. Then we test the shell’s ability to withstand pressure for about 30 seconds, and the examiner will look for any signs of weakness in the fire extinguisher.