Carbon dioxide fire extinguishers are fire extinguishers that use the filled liquid carbon dioxide to spray out fires. It consists of cylinder, bottle valve, injection system and other components. Divided into: (1) Portable carbon dioxide fire extinguishers. The total weight is less than or equal to 28kg, and the specifications produced by Mid-Star are 2kg, 3.5kg and 5kg; (2) Cart-type carbon dioxide fire extinguisher. The total weight is more than 28kg, and its specifications are 20kg and 25kg. Carbon dioxide fire extinguishers are suitable for extinguishing initial fires of various flammable liquids and flammable gases. As well as the fire of live equipment, precision electronic instruments, and valuable equipment. However, it should not be used outdoors when there is strong wind. After using it in a narrow and closed space, it is necessary to ventilate or evacuate the site in time to prevent suffocation.
1. Principle of Carbon Dioxide Fire Extinguisher
Carbon dioxide fire extinguishers are filled with carbon dioxide fire extinguishing agent. Carbon dioxide fire extinguishing agent is usually stored in the fire extinguisher in liquid form. It mainly relies on suffocation and partial cooling to extinguish fire. Carbon dioxide has a higher density, about 1.5 times that of air. Under normal pressure, liquid carbon dioxide will vaporize immediately, and generally 1kg of liquid carbon dioxide can produce about 0.5㎥ of gas. Therefore, when extinguishing a fire, carbon dioxide gas can exclude air and surround the surface of the burning object or distribute it in a relatively closed space, reducing the concentration of oxygen around the combustible object or in the protective space, producing suffocation and extinguishing the fire. In addition, when carbon dioxide is ejected from the storage container, it will be rapidly vaporized from liquid to gas, and will absorb part of the heat from the surrounding, which will play a cooling role.
2. Why Do Carbon Dioxide Fire Extinguishers Have No Pressure Gauge
For most fire extinguishers, whether it is a water-based fire extinguisher or a dry powder fire extinguisher, a pressure gauge is generally installed to detect whether the pressure in the bottle meets the requirements. However, among many fire extinguishers, there is a distinctive type, that is, carbon dioxide fire extinguishers. When checking it, you will find that it has no pressure gauge.
It turns out that carbon dioxide is liquefied and then filled into the cylinder, that is, dry ice. At a certain temperature, the saturated vapor pressure of carbon dioxide is constant, which means that the pressure of carbon dioxide in the cylinder is the same within a certain weight range, even if the gas leaks. The pressure in the bottle is also constant, so it is meaningless to install a pressure gauge. The gas cylinders of carbon dioxide fire extinguishers and carbon dioxide fire extinguishing systems are all checked for air leakage by weighing. The label of the fire extinguisher has the bottle weight and carbon dioxide filling amount data, and the amount of carbon dioxide remaining can be judged by the weighing data and the label data. According to the relevant provisions of "Portable Fire Extinguisher" GB4351.1-2005, the leakage of carbon dioxide gas cylinders should be checked by weighing method. The annual leakage of the fire extinguisher should not be greater than 5% of the rated filling capacity of the fire extinguisher or 50 g (whichever is the smaller of the two).
3. Scope of Application
The carbon dioxide fire extinguisher has excellent properties such as good fluidity, high ejection rate, non-corrosive container and not easy to deteriorate. It is used to extinguish the initial fire of books, archives, valuable equipment, precision instruments, electrical equipment below 600 volts and oil.
Carbon dioxide fire extinguisher is suitable for extinguishing Class B fires, (such as kerosene, diesel, crude oil, methanol, ethanol, asphalt, paraffin and other fires.)
Carbon dioxide fire extinguishers are suitable for extinguishing Class C fires (such as gas, natural gas, methane, ethane, propane, hydrogen and other fires.)
Carbon dioxide fire extinguishers put out Class E fires (fires in which objects burn with electricity).
4. Precautions
It should be placed in a ventilated, dry and cool place, not close to fire sources, avoid strong heat radiation, and strictly prohibit sunlight exposure. The maximum temperature of the place should not exceed 45 degrees to prevent gas loss or safety sheet bursting. The cylinder is rusted.
When handling, handle with care, do not collide, and pay attention to protect the valve and nozzle.
The effect of wind blowing must be considered when using it outdoors, and ventilation should be carried out after indoor use to prevent suffocation.
Once the fire extinguisher is used, it must be refilled.
Maintenance and refilling of fire extinguishers should be carried out by professional units.
