Learn about fire smoke and pay attention to the safety of firefighters

Firefighters spend most of their time working with “fog smoke”. Of course, unlike the gods, they can not “float”. On the contrary, they have to suffer the harm and torment of smoke. More than 85% of those who died from the fire were caused by toxic smoke. As we all know, the main hazard in fire smoke is carbon monoxide (CO), but hydrogen cyanide (HCN) is also an invisible killer in the combustion products. Experiments have shown that high concentrations of HCN can immediately cause firefighters who do not wear air respirators to become poisoned, and even a low concentration of HCN can cause symptoms including fatal heart disease after prolonged inhalation, and studies have shown that in fire smoke There is a synergistic effect between the toxic effects of HCN and CO, two poisonous gases, which means that the simultaneous effect of these two gases will increase the poisoning response of firefighters.

Where does HCN gas come from?

In the past 50 years, the use of plastic products in buildings and internal structures has grown rapidly. The form of fire and combustion products have also undergone tremendous changes. No one will forget the shocking fire that took place in a teacher's apartment on the Jiaozhou Road in Shanghai on November 15, 2010, which ultimately caused 53 people to be killed and more than 70 people were injured. After the accident, Luo Lin, director of the State Administration of Work Safety, said that the accidental use of a large number of flammable materials such as polyurethane foam in the accident site was the main reason for the rapid spread of the fire. In an interview, Zhu Liping, deputy director of the Fire Bureau of the Ministry of Public Security, also emphasized that a large number of polyurethane foam insulation materials on the facade of the building are burning fast and produce a large amount of highly toxic hydrogen cyanide gas, which is the main reason leading to death of many people.

HCN may occur in any fire, whether it is a building fire, a vehicle fire or a forest fire. HCN is generated due to incomplete combustion of nitrogen-containing materials. When the temperature exceeds 315°C, HCN is released as a gas, which is then inhaled by the victim. The study found that cotton will produce 130ug/g HCN after combustion, paper combustion will produce 1100ug/g HCN, and wool fabric will produce 6300ug/g HCN after combustion. It is worth noting that although the fire has been extinguished, the concentration of HCN gas is still high.

HCN and CO gas hazards

Fire products can be divided into three categories: irritating, asphyxiating, and toxic substances that exist in gaseous or solid forms. Although there are numerous chemicals in fire smoke, asphyxiating and toxic substances are often of concern because they are potentially harmful to the health of firefighters.

CO gas in fire smoke can affect the oxygen carrying capacity of the human blood circulation system. HCN gas is 35 times more toxic than CO gas. Once contacted or inhaled, it can affect the internal tissues of human organs, including severe damage to the heart and brain. In a short period of time, people's cognitive ability is reduced or lethargic, which reduces the ability of the victim to escape and the firefighters' rescue ability. When HCN is combined with CO, its poisoning effect will be enhanced and the situation will be worse than when it exists alone. The harm to human body from different concentrations of gas can be given in the following table.

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