One of possible ways to reduce the volume of the use of hydrofluorocarbons (HFCs) as gaseous fire suppressants is studied in the paper. Extinguishing mixtures of HFCs and some fluoroiodocarbons are investigated. It is theoretically predicted that fluoroiodohydrocarbons are effective inhibitors of conversion of fluorinated alkanes in a flame. Special experimental equipment allowing to measure fire extinguishing concentration of gaseous fire suppressant having high boiling point is described. Experiments show that fluoroiodohydrocarbons are effective means of reducing the use of gaseous fire extinguishing agents based on fluorinated alkanes, which are greenhouse gases: in the presence of insignificant addition of iodized substance the volume of fluorinated alkanes required for the extinguishing decreases several times. Creation of mixtures with the content of iodized components higher than 5 mass. is impractical because in this case the iodine-containing substance will exceed safe level of its use from the point of view of toxicity
Calculation of dibromomethane atmospheric lifetime is carried out, as well as an experimental assessment of its fire extinguishing efficiency. Calculations show that methylene bromide atmospheric lifetime is 15.8 days so it rapidly decomposes in the troposphere. The main mechanisms of the removal of CH2Br2 from the atmosphere are its reaction with hydroxyl radicals and the processes of physical removal from the atmosphere. Special experimental equipment allowing to measure fire extinguishing concentration of gaseous fire suppressant having high boiling point is described. Experimentally measured minimum extinguishing concentration of methylene bromide for n-heptane is 2.5 % vol. According to this, CH2Br2 is close to the most effective gaseous fire extinguishing agents, such as C3F7I and C2F4Br2. LOAEL value for CH2Br2 is predicted at the level of 0.3-0.4 % vol. Due to the high boiling point of methylene bromide and its relatively high toxicity, the most appropriate way to use it in fire suppression is to create fire extinguishing mixtures, in particular, with fluorinated hydrocarbons. This approach allows to diminish application of greenhouse gases in fire protection and also to solve the problem of toxicity of extinguishing substance.
Ecological properties of perfluorohexenes are studied in the paper. C6F12 atmospheric lifetime of 17.4 days was obtained using one-dimensional photochemical model. It was shown that the substance disappears in the atmosphere due to its reactions mostly with OH radicals. Absorption spectra of C6F12 in the short-wavelength ultraviolet region of 110-200 nm and in the infrared region were calculated using the Gaussian 09 quantum mechanical calculation program. Calculations revealed that C6F12 has significant absorption in the infrared region but due to short atmospheric lifetime of this substance its global warming potential GWP is as low as 28.64. Ozone depleting potential (ODP) of perfluoroisohexenes is equal to zero due to short chain length for the chain processes of ozone destruction involving fluorine atoms. Thus, perfluoroisohexenes with their zero ODP, short atmospheric lifetime and low GWP meet all modern environmental requirements and can be considered as effective substitutes for high-GWP HFCs in fire suppression.
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