Where should the pressure gauge needle of a fire extinguisher point to indicate normal pressure?
3 Answers
The pressure gauge needle of a fire extinguisher indicates normal pressure when it is in the green zone, with the normal pressure value typically ranging between 1.2-1.5 MPa. If the needle is in the red zone, it signifies insufficient pressure inside the cylinder, meaning the fire extinguisher cannot be used properly. When the needle is in the yellow zone, it indicates overpressure, suggesting the pressure is too high and poses a potential hazard (though slight overpressure may still be considered normal). Specific details are as follows: 1. Combustion Reaction: Fire is a chemical combustion reaction, usually caused by the interaction between oxygen in the air and certain fuels like wood or gasoline. Of course, wood and gasoline do not spontaneously combust simply by coming into contact with air; combustion reactions only occur when the fuel is heated to its ignition temperature. 2. Function of Fire Extinguishers: A fire extinguisher, also known as a fire extinguishing cylinder, is a portable firefighting device. It contains chemicals designed to extinguish fires. The fire extinguisher is a sturdy metal cylinder filled with water or fire-extinguishing materials. When the lever at the top of the cylinder is pressed, the high pressure generated forces the extinguishing agent out of the cylinder, similar to how aerosol cans spray materials. The primary function of a fire extinguisher is to displace air, depriving the fire of oxygen and causing it to extinguish. Since carbon dioxide is a gas and leaves no residue, it is particularly useful for electrical fires to avoid damaging equipment.
The pressure gauge needle on a fire extinguisher must be within the green zone to indicate normal pressure. Typically, having the needle in the middle of the green zone is considered safe. From my fire safety training, I learned that the small dial displays the pressure level: green means the pressure is just right, allowing the extinguishing agent to discharge smoothly; yellow indicates excessive pressure, which may pose an explosion risk; and red signifies insufficient pressure, preventing proper discharge. Each fire extinguisher is marked with a green zone range—for example, dry powder extinguishers usually have a green zone around 10 bar. Regular checks are crucial because temperature changes can cause the needle to drift. Extreme summer heat or winter cold may lead to false readings. I recommend checking the needle position at least once a month to ensure it remains stable in the green zone. Additionally, if the needle wobbles or gets stuck, the extinguisher may have a gas leak or damage and should be replaced promptly. Proper maintenance can effectively prevent fire emergencies.
I always tell my friends that checking the fire extinguisher pressure is simple: if the needle stays in the green zone, it's normal. If it points to the yellow zone, it indicates overpressure, which may pose a safety hazard; if it points to the red zone, it means underpressure and the extinguisher won't work at all. The green zone is a safe range designed to ensure firefighting effectiveness. In my work, we emphasize daily maintenance: don't wait until an emergency to find the needle has deviated. Large temperature fluctuations can easily affect the needle—for example, a garage extinguisher may show abnormal readings on hot days. It's recommended to store it away from direct sunlight and have it professionally tested once a year. Only normal pressure ensures the fire extinguisher is reliable—never overlook this simple step, as prevention is crucial.
