What is a stored pressure fire extinguisher? A fire extinguisher, in which the extinguishing agent and the propelling agent, are contained in one cylinder, in known as a stored pressure fire extinguisher. In other words, there is no second cylinder or pressure cartridge to propel the fire extinguishing agent. These extinguishers are easy to check whether they are in working condition or not, with the help of a pressure gauge fitted on the valve. What does controllable discharge mean? In the obsolete models of fire extinguishers, when they were operated, they used to discharge at once. There was no provision of saving the unused chemical in the extinguisher or to stop the discharge. This was considered as a negative point because even if a little amount of extinguishing chemical was required on a small fire, all the chemical used to discharge, leading to the spoilage of even the material, not on fire. Another point was that if those fire extinguishers were to be carried from one spot to another, like in case of two or three small fires in one room or nearby areas, they used to keep on discharging even in the way from one spot to another. Keeping this in mind, fire extinguishers with controllable discharge were designed so that when there are fires at different spots in a small area, the operator should be able to control the discharge of the extinguisher. This conserved the extinguisher agent for the next fire spot and also stopped the spoilage of the material, not on fire. What is the function of a manometer (pressure gauge)? A manometer is marked with two colored zones, green & red. As long as the needle of the pressure gauge is in green zone, the extinguisher is in working condition. But if it is found to be in the red zone, it as an indication that either the fire extinguisher has been used or the pressure has dropped. In case of dry powder fire extinguishers, when an extinguisher is used partially, and the remaining dry chemical powder is saved, the powder in the fire extinguisher settles in the gasket/washer of the valve of the extinguisher. If this is kept for more than a few hours in the same condition, the gas in the extinguisher, that discharges the powder, keeps on escaping from the cylinder, through the cavity created in the valve of the extinguisher due to the settling of the powder. This ultimately will lead to the complete release of pressure and the needle of the gauge comes to zero. This extinguisher then needs to be recharged. This is why it is recommended, not to use these extinguishers for testing purpose.