ã€Abstract To strengthen the theoretical guidance for the application of positive pressure ventilation technology and improve its application. Based on the research of positive pressure ventilation technology in foreign countries, the advantages and disadvantages of positive pressure ventilation technology are described. In combination with the actual situation of firefighting force emergency rescue, some problems that should be paid attention to in application are put forward.
ã€Key words】 Firefighting Positive pressure ventilation technology Advantages and disadvantages Precautions
A front Words
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Positive Pressure Ventilation ( PPV is the use of a fan to send a large amount of air into a flaming room at a constant flow rate, so that a positive pressure environment is formed in the igniting room, and a large amount of smoke and heat can be quickly excluded from the outdoor through the exhaust port (outside windows). Provide an enabling environment for fire fighting and emergency rescue work.
Positive pressure ventilation was born in the Los Angeles Fire Department in the 1950s. In the early 1990s, the United Kingdom, the United States, France, Sweden, and Finland carried out research on the positive pressure ventilation technology, focusing on the basic principles of positive pressure ventilation, advantages, fan settings, and influencing factors. Application areas and precautions. In 1999 , the survey showed that 42% of British fire brigades use PPV . Researchers predict that by 2001 , the total number of people using PPV will double. Of the 42% of the fire brigade, 27% of the fire brigade used positive pressure ventilation at the beginning of the fire. In the United States, 67% of users use PPV for initial fire suppression. At the beginning of 2000 , most of the German fire brigades used PPV , while in Finland only a few fire brigades used PPV . Today, PPV has become one of the most versatile and effective technologies.
Because PPV can increase the burning rate in the fire zone, it may increase the spread of fire. Therefore, at the scene of fire fighting and emergency rescue, many fire brigades are afraid to use positive pressure ventilation technology. The reason for these phenomena is that fire fighters do not know enough about PPV. There is no systematic understanding of the advantages and disadvantages of PPV and the precautions for using it. Studying the advantages and disadvantages of PPV and application notes are of great significance for further understanding of positive pressure ventilation technology, rational use of positive pressure ventilation equipment, and expansion of positive pressure ventilation.
Second, the advantages of positive pressure ventilation
Since the birth of positive pressure ventilation, researchers in many countries have advanced their advantages. Row The Management s s certificate with real Test research Study . 1985 , PaulGrimwood first proposed and discussed the advantages of positive pressure ventilation. Positive pressure ventilation ( PPV ) is operated by trained and experienced personnel and proved to be a safe and effective method of venting fumes and hazardous gases from fired rooms and buildings. The 1996 Gassby experiment proved that positive pressure ventilation can significantly improve visibility in a short period of time, and put forward five advantages of positive pressure ventilation . 1998 July 28, tactical ventilation experiment fire service school concluded that, due to better visibility, less heat and water damage hazards, PPV faster the fire, firefighters enhance security, improve work surroundings. The IFSTA ventilation guidelines and John Mittendorf acknowledge that PPV is more effective, more comprehensive, and safer than negative pressure ventilation. The National Institute of Standards and Technology ( NIST ) conducted a series of experiments to prove that in the scene of firefighting and rescue, positive pressure ventilation is used to exhaust and remove heat from fired buildings, which can reduce the temperature of the fire area and limit the spread of smoke. Sleepy people provide a more favorable living environment, while increasing visibility, increasing the safety of firefighters, and providing firefighters with an easier to operate environment .
1. Quickly gain high visibility and improve firefighters' work environment
PPV is a simple tactical tool. When it has the application conditions and correct operation, even in the fire extinguishing stage, PPV can improve visibility quickly, greatly improve the firefighters' operating environment, improve people's ability to escape, and reduce construction. Smoke hazards.
Compared with natural ventilation, positive pressure ventilation has higher efficiency and can save firefighters more time for personnel search and rescue and fire fighting. Research at the University of Central Florida has shown that good visibility can be achieved in less than 2 minutes when using PPV ventilation , and 4 minutes with natural ventilation . The experiment of the effect of positive pressure ventilation on the indoor fire also proved that when using the positive pressure ventilation technology to exhaust the building, the PPV ventilation achieved good visibility for 120 seconds earlier than natural ventilation . Increased visibility provides firefighters with further fire detection, search for trapped persons, and facilitates fire operations.
2. Improve the safety of firefighters and trapped persons
The PPV can assist firefighters to reach the fire floor to find and extinguish the fire. Experiments by FFTG have shown that PPV has the ability to exclude or limit the exposure of residents to the toxic gases produced by a fire, so it can open up safety exits and provide firefighters with a safe offensive path.
Another use of PPV is to pressurize a certain part of the building without providing a vent location. Experiments have shown that the correct use of PPV can increase firefighters' fire fighting ability and the survival rate of high-rise building residents. In high-rise buildings, rationally installing fans and pressurizing a stair well to prevent smoke from seeping in can provide a safe evacuation route for trapped people. During the fire clearing phase, PPV can be used to remove the fire gas and pollutants in the compartment to reduce the risk of the firefighters clearing the fire. At the same time, environmental monitoring devices should be used to record the decrease in air pollution to ensure the safety of firefighters. It has been suggested that the use of thermal imaging cameras can detect the location of hot spots safely and effectively, thereby enhancing the effectiveness of PPV .
3. Reduce the possibility of flash fire and reduce the risk
Research shows that PPV can significantly reduce the possibility of flashover. If a victim is trapped between the entrance and the exhaust, the PPV should not worsen the condition and merely increase their chance of survival. The results of Turpin & Bowser ( 20000 ) showed that the human model's skin did not change when the victim was between the entrance and exhaust and used PPV .
4. Wide range of applications
PPV can be applied to various types of fire and emergency rescue scenes. Such as large-scale building fires, underground building fires, high-rise building fires, chimney fires, large-scale aircraft fires, oil depot fires, vehicle fires, and leakage of dangerous goods.
( 1 ) Forming a pressurized staircase or clearing smoke from a high-rise building to help extinguish or evacuate trapped persons in a building;
( 2 ) Remove smoke from the structural facades and improve the environment of external rescue work so that on-site commanders can accurately judge the situation of the fire scene;
( 3 ) To reduce the concentration of CO and other toxic and irritating gases and to improve the safety of firefighters when clearing fires ;
( 4 ) At the site of chemical accident leakage, pollutants in the air can be controlled and reduced, such as the accident site of ammonia leakage;
( 5 ) Where there is a need to limit the spread of fire development, such as in narrow shopping malls;
( 6 ) Larger PPV units can be used to control and reduce fire extinguishing workload in tunnel fires.
Third, the disadvantages of positive pressure ventilation
Although positive pressure ventilation has many advantages in application, it must recognize both sides of positive pressure ventilation at the same time. If the correct use of PPV , will reduce the temperature of the fire field, enhance air mobility, increase visibility, which will greatly improve the firefighters' work environment. . However, PPV may also cause people trapped in the fire scene to further fall into danger, and it is very likely to cause the fire to spread through the wind. Therefore, it must be recognized that the joint use of multiple fire fighting measures in the fire is very important.
1. Accelerate the spread of fire
Because PPV introduces a large amount of fresh air, it will provide oxygen for combustion, and it may cause the fire to expand violently. Experiments have shown that PPV increases the burning rate of the combustion products, and also increases the room temperature in the downwind room (relative to the fan position) in the fire field. Therefore, when people in the downwind direction are trapped, positive pressure ventilation is strictly prohibited. Prior to venting the building using positive pressure ventilation technology, Polycarbonate Corrugated Sheet High Light Pc Sheet,Polycarbonate Sheet Double Wall,Polycarbonate Corrugated Sheet,Polycarbonate Wave Panel SuZhou NiLin New Material Technology Co.,Ltd , https://www.sznlpc-sheets.com