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The present paper explores the change of the harmful factors by means of full-scale numerical models. In the numerical models, the tunnel length is 400 m; the slope gradient varies within 0-9%, with a 2% step; and the heat release rate is within 5-50 MW. The outdoor air temperature on the models was assumed to be 20℃, while the pressure difference between the portals on different models varied depending on the slope, and the variation range was 50-400 Pa. The modeling results show that the propagation of the harmful factors is characterized by stabilization as demonstrated by the fact that the distance of descending propagation of the harmful factors decreases for each specific tunnel gradient and eventually shows a pronounced asymmetry with respect to the seat of fire. This confirms the preferential and pronounced ascending movement of the ventilation flow with toxic products of combustion. Thus, the worst results during the natural ventilation are expected for ascending flows. Based on the isolines of temperature, as well as the concentrations of carbon monoxide and oxygen, the gradient factor can be calculated, which can be used to design ventilation systems for engine tunnels, ensure their safe operation and save human lives during the fire.

The right to life and health of employees is a fundamental right, and the employer is obliged to create safe working conditions. Specifically, ensuring the safest and healthiest working environment for employees is crucial for their well-being and safety. The aim of this article is to assess problematic aspects related to the protection and management of occupational health and safety in the sphere of laboratory medicine. It specifically addresses the evaluation of potential biological, chemical, radiological, and physical hazards in the field of laboratory medicine, their management mechanisms, and preventive measures implemented for risk assessment.

All main and auxiliary equipment in the tunnel with an intelligent ventilation system are designed to ensure the safety. These systems “talk” and “listen” to each other, make decisions to switch on/off certain system(s) or part(s) thereof and duly inform the tunnel operator, who is authorized to the centralized control of all systems of necessity. The present article uses the numerical models to assess the efficiency of the transformable elements ensuring safe operation of the tunnels. The idea of their use is based on an artificial increase of the tunnel aerodynamic resistance by means of a flexible element, which will hamper the dissemination of combustion products, but not the movement of people through the tunnel and will help isolate clean and polluted air masses. Such resistance will be used to swiftly divide the tunnel carriageway into smaller sections what will help extinguish the fire as early as at its initial stage, prolong the evacuation time and save lives during the strong uncontrollable fires. As for the compact transformable element, it can be used in both, the operating and the planned tunnels, as it in practice does not reduce the volume of valuable underground space.

The results of numerical modeling in longitudinal ventilated sloping road tunnels are given. The slope of the tunnels varies in the range of 0-6%. The geometry of the tunnel is as follows: length: 100 m; width: 8 m; height: 6 m; area of the seat of fire: 16 m2. The seat of fire sized: 2.75x5.8x1.5 m is in the central part of the tunnel. The scenarios of development of 5, 10, 20, 30, 50 MW fires are studied in the case of positive and negative directional ventilation flows. The time of modelling was 120 seconds. The numerical problems were modelled with a volumetric grid method. The grid cell dimensions were: 0.5*0.5*0.5 m. Virtual point and volumetric measuring equipment was used to record the modeling results. The modelling used 4 groups of measuring devices that measured and recorded air velocity, temperature, and air and smoke densities. The paper discusses cases of algebraically summarizing the ventilation and fire-induced flows. Based on the results of numerical modeling, we can point out that the widely accepted indices of critical velocity and back-layering length in inclined road tunnels often give erroneous results. Therefore, in strategies for emergency ventilation, indicators such are critical velocity and back-separation should be used with caution.

The work gives the study results for 1:10 scale physical models of the road tunnels. The tunnel slope changes from 0 to 10% with a 2% spacing. As the models show, the fire strength varies within the range of 5 to15 MW with 5 MW increments. The properties of the tunnel geometry in nature are as follows: cross-sectional area: 46.7m2, length: 120 m, width: 8.5m, height: 5.5m and width and height ratio: 1.54. The models are made of 2 mm-thick stainless-steel sheets. We studied the nature of the spread of smoke, the variation of critical velocity depending on the tunnel slope and the characteristic value of such variation - the grade correction factor. The observation over such values is done depending on the air temperature variability in the tunnel model. The measurements are made with K-type thermocouples with open and closed detectors. Maximum temperature measurement is 800°C. The thermocouples are located in the holes provided in the ceiling of the tunnel model. The distance between the holes is 5 and 10 cm what corresponds to the natural length of the tunnel of 5 and 10 m. Fire is modeled by using the natural gas. The indications of thermocouples and air and gas meters are measured simultaneously and the primary analysis and the digital data transmission are provided with a Data Taker DT85 data logger. The gained results may be used to develop ventilation and emergency management projects for transport tunnels as well as to train personnel and rescuers.

The paper considers the spread of combustion products caused by fires with different heat release rates: 5, 10, 15, 20, 30, 50 MW in up to 400 m long tunnels. The slope of the tunnels on numerical models is - 0, 1, 3, 5, 7, 9%. The cross-sectional area of the tunnel is 42.5m2. The paper describes the dynamic variability of damaging factors caused by the “chimney effect” such as carbon monoxide and temperature. Modeling was done with FDS software by using the finite volume method. The time of process modeling is 180 s. The minimum cell size of the finite volume is 0.25x 0.25 x 0.25m. The hearth of fire is in the central part of the tunnel. The obtained results are given in the plane of the central longitudinal section of the tunnel. The boundary condition is given as an increment of the dynamic pressure caused by the height difference between the portals in normal conditions. The dependence of fire-induced backlayering distance on the fire heat release rate and the increment of the dynamic pressure caused by tunnel inclination are studied. The theoretical results and those obtained by modeling of the backlayering distance and velocity are analyzed and compared. The locations of high-risk factors for each damaging factor along the tunnel are identified. Their quasi-stationary nature is described and the intervals of transient processes typical to each factor are determined in the course of modeling. It is advisable to use the obtained results to respond to emergencies caused by fire in relevant tunnels.

Protecting the infrastructure of the metro from unauthorized actions with the help of ventilation openings of the systems is one of the main security problems of this type of transport. This article discusses the problem of the dynamics of distribution of the mass flow rate of ventilation air in a two-component system “tunnel vertical ventilation shaft”, due to the piston effect of a moving train. The dependence of the mass flow rate of ventilation air passing in both directions in short ventilation shafts (up to 10 m), on the speed, location of the rolling stock and cross-sectional area of the ventilation shaft is investigated. It is shown, that at speeds of 10–20 m / s of rolling stock and sections of the ventilation shaft of more than 4 m2, the mass flow rate of air passing through the ventilation shaft must be taken into account with the mass flow rate of ventilation air in the transport tunnel for assessing the safety of the harmful aerosols. These processes can have a significant impact on the air quality of the underground infrastructure of the metro.

Heat, smoke and other toxic products may spread along the tunnel, in both directions from the seat of fire, causing different kinds of damage to people. Anyway, underground fire causes complicated results, which is preventing factor for life rescue and evacuation, creating difficulties for firemen and life rescue crew. Analysis of the critical speed, which is necessary for the effective management of combustion products, has been made for tunnel fires with high heat release rate. The characteristic changes in the critical Froude number in the work are presented in accordance with the critical speed. Particularly, it was noted that the formula determining the critical speed requires knowledge of the average smoke temperature, while the formula for calculating the last value includes the value of the required critical speed. In order to overcome this, Froude’s critical number Frc=4.5 has been introduced, which is not the way of solution, as it directly means constant critical velocity for the fire of any power and accordingly, does not correspond to experimental data.