Currently, the scope of the methodology of risk analysis continues to expand. With regard to the emergency (fire in particular) it's more correct to speak about security analysis and quantitative risk assessment (QRA). Accidental risk metric that describes a probability and accident damage, it should express the scalar number. There are four most important issues of this methodologies today: • imperfection of the existing methodological framework; • staffing (human resources); • absence of federal criteria of acceptable risk; • presence of uncertainty on all stages of the QRA. Despite the fact that around the world the presence of uncertainty and methods of its quantitative assessment in the performance of the QRA has long been widely studied, this problem is ignored in Russia. Uncertainty has two aspects - quantitative and qualitative. Analyzing the sources of uncertainty, it decided to allocate the following types: terminological, parametric and model. The latter, in turn, are subdivided into scenario, conceptual and approximating. One can cite a few concrete examples of the different types sources of uncertainty of fire risk. According to the analysis, the greatest uncertainty is accompanied assessing the likelihood of events and stage assessment of the damage. In the latter case it is possible to allocate uncertainty of qualitative and quantitative type.

There are considered two typical schemes of the thermodynamic picture of the fire when burning solid and liquid combustible substances and materials: the combustion process with the use of exhaust ventilation to remove combustion products from small-scale chamber and fire in a full-scale room with a small square of holes or at the initial stage of fire, when through the openings occurs only a displacement of the gaseous environment of the room to the outside. It is presented the analytical dependence for the calculation of the average volume density of toxic gas in the case of the above mentioned schemes of fire development. It is shown that the density does not depend on the properties of the combustible material, the size of the room and exposed surface area of combustible material. Three-zone mathematical model of initial stage of fire in the room is described. Small-scale pilot plant is created for realizing the combustion process with the use of exhaust ventilation to remove products of combustion. The results of calculations of the carbon monoxide density, obtained for full-scale fire using analytical solution of the integral model and zonal mathematical model, are compared with the experimental data. It is shown that the calculations of densities of toxic gases in full-scale room can be performed taking into account only the experimental dependencies of the above mentioned densities from the temperature without using specific coefficients for the release of toxic gases. The accuracy of such calculations is sufficient to solve practical problems. On the basis of obtained results it is suggested a new approach to the calculation of the spread of toxic combustion products during a fire in a full-scale room, which, unlike traditional, is the following: • it is conducted experimental research of combustible material in the proposed small-scale pilot plant with the aim of obtaining dependencies between average volume densities of toxic gases and temperature (up to 70 °C); • dependencies volumetric average temperature (integral model) or volumetric average temperature of under ceiling layer (zonal model) on the time the fire started are calculated, as well as the value of the coefficient of heat losses; • the corresponding average volumetric densities of toxic gases are defined by the corresponding obtained experimental curves using the calculated average volume temperature or average volume temperature of under ceiling layer for each point in time of fire.

Data shown in the article give evidence that car fires refer to extremely serious accidents, therefore the problem of car fire safety enhancement is very topical. In this connection development of measures for car fire prevention is of great importance. One of preventive measures is fire investigation. In the article it is stated that them majority of conclusions of expert fire engineers regarding technical reasons for car fires has presumable (probable) nature which does not allow developing and implementing exact engineering solutions. This maybe explained by many reasons including absence of scientifically based methods. In particular, the problem of identifying primary, secondary short circuit or current overload in fusing copper conductor is not clearly solved, even though attempts to solve this problem using instrumental methods were made by criminalists starting from the 50^s of the last century. The article gives results of studying fracture surfaces of copper conductors exposed to high-temperature, secondary short circuit and current overload. To conduct study we used raster electronic microscope JSM-6390LV. It has been proved that on the fractures surface of copper conductors specific features for such as high temperature, secondary short circuit, current overload may occur in form of cell-type relief, microporosity, appearance ball-shaped microfusion around microcracks, steps on the fracture surface. Identification of such features allows identifying reason for destruction of copper conductor in case of fire and significantly simplifying determination of fire reason. It is found that the determined reasons are stable and not subject to changes in natural conditions of storing thermally damaged car. Data given in the article may be used by specialists in expert investigation of 12 V electric circuit copper conductors taken from fire locations, in identification of damage nature and, finally, in determination of car fire root cause.

The detailed analysis of different ways of testing water and foam sprinkler automatic extinguishing systems (AES) during the process of their operation, including an analysis of the methods contained in normative documents and patents was practiced. It is noted that test methods, mentioned in the national standards, do not meet the set objectives in a full range. It is shown that methods used in current standard, based on the examination of the sprinkling intensity in the three measuring jars, placed in the most unfavorable areas for irrigation, are imperfect during the actuation of one sprinkler or four drenchers. Usage of one sprinkler or four drenchers on a chosen area for examination of a sprinkling intensity cannot identify a real operability of AES even in the case of positive test results, because the pressure of a single most remote actuated sprinkler is much higher than the pressure of all the actuated sprinklers protecting the calculated area. In addition, the larger a calculated area - the more appreciable this difference is. However, the higher the pressure-the more the sprinkling intensity is. Besides, in real conditions during the actuation of a design quantity of sprinklers the AES flow rate, consequently its sprinkling intensity, can be lower than planned ones because of various conditions. But this failure cannot be detected during the operation of one sprinkler. Positive results of sprinkling intensity tests in the three measuring jars do not guarantee that there will be a design intensity in the limits of 12 m² protected area, where these jars were absent. That is why there is no need in testing the AES with the flow of extinguishing agent directly on the protected object and measuring the water sprinkling intensity; there is no need in bearing fire tests of the installed AES on a protected object. Integral ways of examination of water AES via imitation of the highest remote section area of a sprinkler AES or the highest remote section area of a drencher AES were suggested. Data noted in this article belong to water AES corresponded GOST R 50680-94 and to foam AES corresponded GOST 50800-95 as well, according to test methods. Mentioned standards need a total revision in test methods section parts.

Ability of fire extinguishing agents to absorb half of the heat flow escaped while burning, that can lead to flame extinction, raises doubts in calculation of the thermal balance of a powder and, further, of sprayed water. It turned out that the balance of heat has a big advantage towards heat escaped during flame combustion. Amount of powder or sprayed water become insufficient to absorb half of the heat flow of flame. This work contains data and results of complex experimental and theoretical researches of the process of extinguishing of the flame of hydrocarbons by various types of fire extinguishing agents, including sprayed water, fire extinguishing powder, reactive freon and low expansion foam. On the basis of experimental researches of the process of extinguishing by means of streams of dispersed extinguishing agent and low expansion foam it is offered and substantiated the "local" mechanism of suppression of a flame of liquids by extinguishing agents. Existence of the minimum on curves of dependence of specific consumption on flow rate in the area of optimal flow rate of extinguishing agent is experimentally shown and theoretically substantiated. It is also offered two-stage mechanism of suppression. The first stage consists in interaction of the stream of extinguishing agent with part of a flame jet which is in contact with front of extinguishing agent. The flow of extinguishing agent interacts only with a small (local) area of the flame. Fire extinguishing agent allows not only to absorb half of the heat from flame jet in a local part, but also to cool it practically up to the temperature close to water boiling point. It leads to termination of burn directly on the front of movement of a fire extinguishing stream. Such "local" mechanism of interaction of sprayed water stream leads to evaporation of larger or smaller part of sprayed stream depending on its dispersion degree. The second stage of suppression process provides spreading of water vapor, as a layer of certain thickness, over the burning surface. The higher dispersion degree of sprayed water, the larger volume of water vapor and higher it's covering rate of burning surface. Such extinguishing mechanism is also implemented in case of application of sprayed freon, sprayed powder, solid aerosol and low expansion foam. Standard equations for calculation of time and specific consumption of different types of extinguishing agents during suppression of flammable liquids are proposed. Satisfactory congruence of experimental results with data obtained by calculation using formulas which correspond to the "local" mechanism of suppression of a flame by fire extinguishing substances is shown.

Atomized water sprayer advantages and fields of their application have been shown. Fine dispersion droplet flow characteristics most vital for firefighting such as averaged flow droplet diameter, spray intensity and flow rate, were determined. A new class of atomized water sprayers that mainly employ cavitation effects in channels and liquid vortices has been illustrated. Sprayer prototypes fully complying with atomized water flow dispersion characteristics were designed and tested (D₁₀ < 150 |im at pressure more than 0,4 MPa). AFFF-type foam agent additive to water wouldn't distort their hydraulic, electrical, and dispersion features. Firing tests on model fire site of liquid and solid combustibles demonstrated high fire extinguishing efficiency with a new class of sprayers applied, thus achieving model fire site extinction that wouldn't be suppressed by standard conventional sprayers. Electrical safety margins have been determined by live equipment spray intensity J< 0,4.. .0,71/(m² •s) with a new sprayer class used at 0,4.1,0 MPa delivery pressure.

The article gives a review of extinguishing fires of oil and oil products at oil production facilities, in particular extinguishing flames of oil and oil products with fire extinguishing foam, produced from foam forming agents of various nature. The objective of this work was to conduct a series of comparative tests to determine fire extinguishing efficiency of foam, produced from various fluorine containing foam forming agents. As a result, there were studied foam forming agents of both domestic and foreign manufacturers as well as fire extinguishing efficiency of those foam forming agents was identified. Based on the results of the experimental studies comparative data regarding critical and optimal intensity of foam supply for all foam forming agents under the study was obtained. The data obtained can be used to provide fire protection at oil production facilities and for more efficient fire extinguishing at those facilities. Main conclusion from the tests conducted is availability of minimum specific flow of foam forming agent aqueous solution based on the intensity of foam supply for all foam forming agents under study which allows to identify optimal intensity of foam supply, necessary for successful fire extinguishing of oil and oil products.