It is known (Eckhoff, 2003) that an experimental study of aero-suspension of dust with low explosivity in a 20-liter chamber leads to overestimation of the explosion. A special concern is the risk of a qualitative error, when non-explosive dust will be transferred to explosive dusts, which will cause unjustified costs for ensuring the safety of industries involving this dust. This work is aimed at reducing this risk. In this work, a quantitative analysis of the causes of overstatement of dust explosiveness is performed. It is shown that the testing of dust/air mixture in a 20-liter chamber does not correspond to the normal initial conditions of the investigation (pressure 100 kPa, temperature 25 °C) stated in the methodologies and, in fact, is an explosion hazard study of dust/air mixture with an increased initial temperature and an increased initial pressure in the chamber. Two processes lead to an increase in the initial temperature: the dispersion of particulate material in the chamber by a pulse of compressed air from the receiver; adiabatic compression of dust/air mixture upon activation of the ignition source and local burning out of the dust found in the flame and/or near the flame of the ignition source. The latter process leads to an increase in the initial pressure in the chamber. The implementation of this analysis required the development of a reliable criterion for the explosion of dust, since there is still no single idea of such a criterion, judging by the norms of the United States and European countries. The new criterion is based on two assumptions: (1) on limiting the variety of the development of dust ignition in two scenarios (Cashdollar and Chatrathi, 1993) - local burning out of dust in some neighborhood of the ignition source and dust explosion, covering the entire volume of the chamber and (2) on the essential difference between pressure jumps in the chamber, expected for different scenarios. Two variants of application of the results of this work are demonstrated. First, it is possible to forecast the conditions under which an explosive danger arises in the dust, which is not explosive under normal conditions. Such a forecast is made in case of recording the explosion of this dust in a 20-liter chamber and assessing the real initial conditions of the study. In particular, an explosion of anthracite, investigated in a 20-liter US Bureau of Mines, is predicted to be explosive at a temperature of 140 °C. Secondly, it is possible to outline ways of realizing the conditions for experimental investigation of dust with a low explosivity, close to normal. They will significantly improve the reliability of the conclusion about the low explosiveness of combustible dust without the use of large-scale equipment. Two such methods are proposed in the work. The first method is based on the reasonable assumption that for a dust with a low explosion hazard low oxygen concentration LOC » 0.21, and the known empirical linear dependence of the explosion index K_st on the oxygen content in air. Within the framework of this method, a search is made for the LOC, by examining K_st for dust suspensions in air enriched with oxygen. The explosion hazard of dust is judged by the ratio between the extrapolation obtained by the LOC and the usual oxygen content in the air (0.21). The second method involves a modified design of a 20-l camera, which differs from the standard design of a 20-liter chamber in a vertically extended shape and variable volume. The latter is achieved by using a “flexible” top end of a polymer film, initially concave into the chamber, but assuming a convex shape after dust dispersion and triggering the ignition source.

The article raises the topical issue - the lack of physical and chemical properties of new synthesized substances. These properties will allow supervisors to develop fire safety systems at security facilities. The efficiency of such systems is achieved by eliminating the combustible environment or the ignition source. Using the example of esters of butyric acid, which are used practically in all areas of industry and produced according to reference data in the amount of more than several tens of millions of tons per year, it was possible to predict one of the most important fire hazard properties of a substance - the self-ignition temperature, using the technique for predicting the fire hazard properties of refined products based on molecular descriptors and artificial neural networks. The proposed methodology is implemented with the help of the author’s computer program “NeuroPacket KDS 1.0”. The program “NeuroPacket KDS 1.0” allows you to: download and view databases containing chemical compound structures and their properties; to correlate the input data; statistically evaluate the resulting models; use the obtained neuronet models to predict the properties of substances without conducting a complex experiment. This approach to predicting the fire hazard property of oil refining products describes the structure of the molecule with the help of molecular descriptors and establishes quantitative correlations between the values found using artificial neural networks. Based on some reference data, data was verified. Analysis of the results obtained showed that the average relative error does not exceed 3 %, which is a good indicator. In addition, the autoignition temperature of esters of butyric acid was predicted, information on which is absent in the reference and regulatory literature. This makes it possible to build on the values obtained in the development of fire safety systems. Based on the obtained results on the self-ignition temperature of the substance, there were determined the temperature classes of the explosion-proof electrical equipment, which, on the whole, ensures fulfillment of item 4, article 50 of the “Technical Regulations on Fire Safety Requirements” (Federal Law No. 123). It is also worth noting that the methodology for predicting the fire-hazardous properties of oil refining products based on the use of molecular descriptors and artificial neural networks allows us to conclude that this technique can be used to predict other fire-hazardous properties of organic substances.

Introduction. Epoxy oligomers are widely used as binders in construction industry. At the same time, wide use of polymers in modern construction industry requires careful examination and optimization of operational properties related to fire safety. It is known that such properties can be controlled by chlorinated paraffins, synthesized fire retardants of type “Redant” and many other compounds. However, the effect of such compounds to the properties of epoxy matrix composites has not been thoroughly investigated to date. The choice of an admixture that reduces the fume evolution of epoxy composites is an important task also. Purpose of the work. The purpose of this work is to study the thermal stability, flammability, fume evolution of epoxy matrix composites with different types and amounts of hardeners, fillers, plasticizers, fire retardants and ferrocene derivatives. Materials and methods. Dependencies between thermal stability, flammability, fume evolution of polymer matrix composites based on ED-20 epoxy resin and amount and chemical type of components are examined in the present work. To control operational properties of interest the chemical type and content of hardeners, fillers, plasticizers, fire retardants and ferrocene derivatives are varied. DuPont-9900 device is used for thermal analysis. Properties related to fire safety are determined in accordance with RU GOST 12.1.044-89 and several methods that were previously developed by authors of this work. Results. It is shown that while phosphate-based plasticizers are of almost no effect on combustibility of epoxy-based polymer matrix composites, they can successfully be used for the reduction of fume evolution. It is revealed that chemical nature of mineral fillers has little effect on the flammability when amount of such fillers are less than 45 % by weight; at the same time, fume evolution linearly decreases with the increase of degree of filling. To reduce the flammability of epoxy composites, we propose additive bromine-containing flame retardants in the form of a solution in N,N-dimethyl-2,4,6-tribromoaniline. High efficiency of acetylferrocene and a-hydroxyethylferrocene as reducers of fume evolution is shown. The correlation between critical density of the heat flux of ignition and limiting oxygen index and also limiting concentration of oxygen is revealed. Conclusion. In the present work we have summarized results of several laboratory tests. The tests were allowed to select the type and amount of components of epoxy matrix composites with improved operational properties, intermediate and small combustibility. Such composites can successfully be used in different areas of construction industry.

This paper presents the results of research of influence on physical, mechanical and fire properties of wood to its impregnation with the use of three fire and bio protective systems: 1. The system is based on the solution of inorganic nitrogen - phosphorus-containing compounds (composition 1). 2. The system is based on organic nitrogen-phosphorus-containing compounds, which was used as the commercially available fire and bio protective composition Ammofon-1 (composition 2); 3. The system is based on organic film-forming intumescent substances, which was used as a product of oxidation of plant polysaccharides (composition 3). The obtained results demonstrate that the introduction of the fire and bio protective compounds in the wood structure is the most positive effect on such indicators of fire hazard such as flammability and ability to spread flame over the surface. At the same time, the levels of absorption (from 25-30 kg/m³) do not lead to deterioration of physical and mechanical properties that says about the prospects of using the method of deep impregnation to reduce the fire hazard of bearing and enclosing structures made of wood, eliminating the possibility of the development of latent combustion and rapid development of the fire. The most difficult issue is the reduction of smoke generation ability and toxicity of combustion products, to reduce which it is necessary to enter in the structure of the wood compounds in excess of commercially reasonable levels (more than 40 kg/m³). Moreover, in this case may indeed be some degradation of physical and mechanical properties of wood and its adhesion properties. At the same time, the excess impregnation can effectively be used for decorative layers of glued structures, or when using wooden elements (do not perform structure functions) in the decoration of the premises, including emergency exits. In this case, given the generally small size wooden finishing elements, the excess impregnation does not pose any technological difficulties. The results of the work determined control values, characterizing the influence of absorption level on the physical, mechanical and fire properties of wood (see Table).

The theoretical and experimental study results of finely-dispersed water droplet flow features screening fire heat radiation are shown. Water curtains offer cooling and fire with its danger factor spread prevention (OFP) through window, door and technological openings, outside protected equipment, area or rooms, as well as safe people escape provision from rooms on fire. In designing water curtain generation devices, as a rule, there aren’t taken into account curtain parameters defining their protection features, such as screening factor, droplet diameter and their concentration. Fire protection curtain efficiency depends to a lesser extent on fire temperature but to a greater extent it depends on water droplet diameter and water flow rate. A relatively efficient and water flow-rate-effective curtain can be designed with sprayer generated droplets of less than 200 mm diameter. With droplet size of more than 500 mm the infra-red fire radiation is screened by less than 25 %. Single-fold dispersion for finely-dispersed water with r = 20 mm droplet radius and n = 10¹⁰ m^-3 droplet calculated concentration is possible in a few centimetre length. In considering screening curtain features the average Zauter diameter d₃₂ plays an essential role, particularly it refers to a multiple dispersion that considerably (by 4…5 fold) decreases radiation falling onto the screen. Fine droplets usage d₃₂ < 100 mm in diameter is connected with certain features of that flow. This also relates to an output sprayer nozzle, the diameter of which greatly effects the size of generated droplets: the less the nozzle diameter, the less average Zauter diameter of the droplets in the spray cone. A great droplet diameter dependence follows from output sprayer nozzle liquid velocity value that turns into a droplet flow while interacting with the ambient air, thereby the greater an output liquid velocity, the smaller the droplets. The experimental data analysis shows that infra-red radiation shade coefficient increase is connected with volumetric droplet concentration (curtain flow rate), and average median diameter decrease (droplet flow dispersion).

Introduction. Peat deposits are found in many places around the world, but the world’s largest peatlands are the West Siberian Lowland, the Hudson Bay Lowland, and the Mackenzie River Valley. Peat fires are significant sources of carbon dioxide (a greenhouse gas) and carbon oxide (a toxic gas). In addition, peat fires release mercury into the atmosphere at a rate 15 times greater than upland forests, which may be a serious human health concern. If a peat fire develops near a highway, the smoke from the burning peat-bog reduces the visibility, makes the breathing difficult, affect the human nervous and cardiovascular systems and may finally result in traffic accidents or in an emergency. Modelling methodology. K-theory approach . According to Berlyand, such parameters as instant concentrations of CO pulsed deviations from these values and the velocity of the CO diffusion should be taken into consideration while developing an emission model of the peat deposits burning near the highway. The problem is simplified by the application of the turbulent diffusion model. Using this approach, also known as K-theory, together with reasonable approximations and assumptions, there was established that the concentration of the pollutant emitted from the unregulated square source, such as a burning peat bog, is as follow in the Russian normative document OND-86. At the same time, this approach is time-consuming and doesn’t specify inaccurate problem parameters derived from the measurements. To solve these problems, we offer to apply a neural network approach. On the base of the measurements, there was developed a neural network model with parameters (weights) tuned via optimization methods. The RProp method and the combination of “cloud” and RProp methods were in use. The neural network model of the complex system can gather pieces of heterogeneous information - differential equations, conservation laws, equations of state, symmetry conditions, etc. The information exchange via neural network parameters between different levels of hierarchy makes computing less resource consuming. Results and discussion. Case study 1. Visualizes the joint results of experimental and simulated measurements of the peat fire-related CO concentrations near the Federal Highway R-255 “Siberia”. The concentrations of CO are expressed in terms of Limit Value Units: 20 minutes CO limit value is 5 mg/m³. The calculations were realized using the software program Ecolog 4 (Integral Co. Ltd., Saint Petersburg, Russia). The results of the measured and simulated CO concentrations reaching values of 0,8-1,2 mg/m³ were later used as input heterogeneous data for the calculations by the neural network technique described above. Case study 2. Turbulent diffusion loses importance when modeling the transfer of the smog clouds from the peat fire over long distances. In addition, there is possible not only a smouldering peat fire but a burning peat fire followed by the emission of hot gases. We have developed an original neural network model, based on the Gaussian dispersion, to estimate these physical phenomena. Assume that the average cross-section of a peat fire smog cloud, migrating in the vicinity of a highway, is similar to the Gaussian distribution having a plume profile. Show’s the dynamic development of the pollution in this area at the wind in the direction of the highway (4 neurons). Parametric model allows predicting the level of peat fire-related air pollution at different wind directions (Project No. 14-01-00733-А supported by the grant of the Russian Foundation for Basic Research).