The danger of fire is not only direct damage such as heat and explosion, but also indirect damage caused by smoke and lack of oxygen. In order to reduce the toxic hazards caused by smoke in fires, the prerequisite is to evaluate the toxicity of tobacco production of relevant materials, which is very important in all walks of life. Today, Cheng Cheng Xiaobian will interpret the tobacco toxicity of materials according to relevant standards.
The current national standard GB/T20285-2006 Classification of Tobacco Toxicity Risk of Materials stipulates the grades, test devices and test methods for the risk assessment of tobacco toxicity of materials. This standard is applicable to the hazard classification of flue gas toxicity for stable tobacco production, but not to the hazard classification of flue gas toxicity for unstable tobacco production.
The standard adopts a ring furnace with constant velocity carrier gas flow and stable heating supply, and the strip specimens with uniform quality are heated at constant velocity mobile scanning and heating, which can realize the stable thermal decomposition and combustion of materials and obtain a flue gas flow with stable composition concentration. In general, the same material is most toxic when there is full smoke production and no flame at the same smoke production concentration. For different materials, the animal toxicity test is carried out with smoke under the condition of full smoke production and no flame, and the smoke production concentration required by the experimental animal to reach the test endpoint is used as the basis for judging the tobacco toxicity risk level of the material - the lower the required smoke production concentration, the higher the tobacco toxicity risk of the material, and the lower the tobacco toxicity risk of the material with the higher the required tobacco production concentration.
There are three levels of tobacco toxicity hazards in materials: safety level (AQ level), quasi-safety level (ZA level) and dangerous level (WX level). Among them, the safety level and quasi-safety level are further subdivided according to the lower limit of concentration.
The standard stipulates that the test endpoint of the level determination follows the following requirements: a group of experimental mice shall be tested for 30min according to the concentration of the level specified in the above table with the smoke of the material reaching sufficient smoke production rate, and the following judgment shall be made according to the test results, if a group of experimental mice do not die during the poisoning period (including within 1h after infection), the material shall be judged to be anesthetic qualified at this level; If a group of experimental mice do not die and have no weight loss after 30 minutes of poisoning, or although the body weight has decreased, the average body weight within 3 days has recovered or exceeded the average body weight at the time of the test, the irritation of the material is judged to be qualified at this level; The highest concentration level that is qualified for both narcotics, and irritation is set as the smoke toxicity hazard level of the material.
Cheng Cheng's conclusion: In addition to the common combustion rate and other combustion indicators, the combustion performance of materials is also very critical. Due to the difficulty of the test of tobacco toxicity and the long period of testing and observation, there are few testing institutions with testing capabilities, and the test cost is relatively high, so it is often ignored. When sourcing and using materials, especially those that claim to be flame retardant, it is important to pay attention to the tobaccogenic toxicity of the materials, which is essential from a safety point of view.