Toxicity analysis and smoke prevention measures of

Toxicity analysis of fire smoke of polymer materials and its smoke prevention measures

this material was originally developed for the furniture industry. With the rapid development of science and technology and the construction industry, polymer materials are changing and improving people's living standards at an unprecedented speed, and are widely used in building decoration, decoration materials and furniture manufacturing. However, because most polymer materials are flammable (B3 level) or flammable (B2 level) materials, they will decompose and burn when encountering high temperature in use, and the heat release rate is high, which is very easy to cause fire and produce a large amount of toxic smoke, which hinders the safe evacuation of personnel and the fire fighting and rescue operations of fire forces, resulting in huge casualties and economic losses. Take the end of 2007 as an example, in less than three months, there were three serious and catastrophic fires that killed more than 10 people in a row across the country: on October 21, 2007, a fire broke out in a shoe upper processing plant in Putian, Fujian, causing 37 deaths; On December 12, 2007, fires broke out in Wenfu building in Wenzhou, Zhejiang Province and Zhangmutou cafe in Dongguan, Guangdong Province, killing 21 people and 10 people respectively

a large number of fire cases at home and abroad show that 70% - 80% of the fire deaths are directly poisoned by smoke, which mainly comes from the combustion of polymer materials in the fire; Most of the other victims who were burned by fire were also smoked down by toxic smoke before being burned to death [1]. Therefore, the prevention and control of fire smoke from polymer materials has become one of the major issues that the current fire department urgently needs to study and solve. In this paper, the classification, smoke toxicity and release law of polymer materials are discussed

I. main components and toxicity of flue gas

flue gas is also called smoke, which is a mixture of suspended solids, liquid particles and gases generated during the combustion of combustible substances. 4. When the cable voltage withstand test is carried out in phases, its particle size is generally 0 Between microns, its composition and properties mainly depend on the chemical composition and combustion conditions of the combustion substances. People often say, "the wind borrows from the fire, and the fire borrows from the wind." In fact, for the trapped people in the fire, smoke is more harmful than fire; When the building was on fire, the fire dragon was far away, All pervasive smoke "kindergarten working procedures" pointed out: "Kindergartens should adjust measures to local conditions and use local materials. Gas has already begun to be violently abused. Because the substances involved in the combustion in the fire and the environmental conditions of the fire are relatively complex, especially the wide application of polymer materials in the construction, decoration and furniture industry, the large amount of toxic gas produced by its combustion makes the toxicity of fire smoke increasingly serious, and has become the main cause of death on the fire site, which is vividly known as "The first killer in the fire". Typical cases in China are: on November 27th, 1994, a fire broke out in the Yiyuan song and dance hall in Fuxin City, Liaoning Province, killing 233 people and injuring 16 people; On December 8th, 1994, Xinjiang Karamay friendship hall fire killed 326 people and injured 134 people; On December 25th, 2000, a fire broke out in Dongdu commercial building in Luoyang, Henan Province, killing 309 people. Statistics from the United States show that in the past 40 years, smoke inhalation death accounted for 70% to 75% of the total number of fire deaths, and this figure has an upward trend [2]

the combustion reaction of polymer materials generally goes through the high-temperature decomposition of polymer chains and the combustion reaction of decomposition products. Different polymer materials have different decomposition modes at high temperature, but the results are that a variety of small molecule hydrocarbon intermediates are generated and high-temperature combustion reactions occur. The experimental results show that due to the large temperature gradient and insufficient oxygen supply in the fire, polymer materials and their additives (such as plasticizers, anti-aging agents, preservatives, flame retardants, etc.) often burn incompletely during the combustion process, resulting in a large number of toxic gases, including Co, C02, S02, NH3, CH4, HCN, HCl, etc., of which CO, C02, HCN are the most important gases causing death in the fire [3]

co's harm to human body mainly depends on its concentration in the air and contact time. The binding ability of CO to heme (protein) in red blood cells is times that of oxygen (another data), which will preempt the combination with heme to form carboxyheme (carbon monoxide heme, COHb), lose oxygen carrying capacity, and cause tissue asphyxia. After exposure for 1h, the safe volume fraction of CO is 0.04%-0.05%, and the volume fraction of CO during evacuation is not allowed to exceed 0.2%. However, at the initial stage of the fire, the volume fraction of CO in the smoke is as high as 1%, and at the development stage, the volume fraction of CO is as high as 4%-5%, up to 10%, which can cause people to die instantly [4]

co2 itself has significant toxicity only when the volume fraction is high, but the toxicity is more serious under hypoxia. The normal volume fraction of C02 in the air is 0.03%. The volume fraction of C02 in the fire site can reach 15%-23%. Animal experiments showed that under the condition of normal oxygen content (about 20%), the volume fraction of CO2 increased, and the animal mortality increased; In the gas with low oxygen (5%), 1/10 animals can die; However, under the condition of hypoxia (5%), containing 11% CO2 can make all animals die within 60min [4]

hcn (hydrogen cyanide is recognized and widely used by customers) is the fastest and most toxic cyanide. It can make the human body lack oxygen, inhibit the production of enzymes in the human body, prevent normal cell metabolism, and cause asphyxia in the body tissue. After inhaling mg/m3 for several hours, people have mild symptoms; After inhalation of mg/m3, 0 Hour death; When it reaches 300mg/m3, it will die immediately. At the same time, when hydrogen cyanide and carbon monoxide exist at the same time, their toxicity is additive [5]

in addition, a large amount of smoke will also make the oxygen content in the fire site lower than the value required by people's physiological normal. In most cases of fire, the effect of oxygen volume fraction reduction is secondary to that of Co. However, the fire experiment of limited space shows that the situation of hypoxia will further develop in the fire. When the volume fraction of oxygen reaches 10%-15%, it is a critical state, below which it will have a serious impact on personnel safety; If the volume fraction of oxygen is less than 6%, people will suffocate due to severe hypoxia within a period of time. At the same time, in the anoxic fire environment, the content of CO will increase. At this time, the oxygen in the blood will be in the dual anoxic state. This anoxic state, combined with the toxic effect of heat, smoke and other gases produced by the fire, may cause more serious harm to the human body [3]