THE REASONING OF CORRECTIVE COEFFICIENTS FOR DETERMINING THE TIME OF PROTECTIVE ACTION OF SELF-CONTAINED BREATHING APPARATUS FOR FIREFIGHTERS

Abstract

According to regulatory requirements and rules of safety work, every firefighter who works in the SСBA while working in a gasified and smoke environment should monitor the readings of the pressure gauge and be able to calculate the air consumption (oxygen) and the duration of work in the SCBA. The main indicators that are taken into account during calculations of working time in gaseous and smoke environments are control pressure of air (oxygen) into the SCBA, in which it is necessary to go out to fresh air; working time in gassed and smoke environments; expected return time to fresh air. The supply of air will directly depend on, firstly, the volume of the cylinder (cylinders) and the working pressure, secondly from the working conditions and physiological features of the firefighter. Since, in determining the average work time of firefighters in SCBA in a gasified and smoked environment, according to the formula specified in the regulatory requirement, the capacity of the SCBA cylinder has not taken into account, the purpose of the work was to determine the correction coefficients, which would consider this. Considering the providing of fire rescue units of the SES of Ukraine with SCBA, we can conclude that the largest number of SCBA in the operative calculation, this is the SCBA of leading European firms, namely Drager and MSA AUER. The analysis of the load of the work of the firefighters in the gasified and smoked environment has shown that 50% is the work of the average degree of gravity corresponding to pulmonary ventilation of 40-liter per minute. Analysis of the technical characteristics of the SCBA of Drager and MSA AUER firms has shown that in this SCBA, the same performance of the pressure demand regulators 40-liter per minute and working pressure P = 300 bar. However, different capacities of cylinders 6, 6.8, 7 litres, respectively, which definitely affect the supply of air that is necessary for the work of the firefighter. Fire Safety, №34, 2019 65 Therefore, having performed the calculations of the average time of operation of the firefighters in SCBA link in the gassed and smoked environment in two formulas. The first one - according to the regulatory requirement defining such calculation, the second – according to Boyle–Mariotte law, which takes into account the cylinder capacity, working pressure and air consumption at medium load, we got the following data:  for cylinders of 6 l capacity, this difference is not significant (only 2 minutes), which is only 5% of the error, thus the correction coefficient to the base formula is not required;  for cylinders with a capacity of 6.8 litres this difference is significant (7 minutes) which is 20% of the error, respectively, the introduction of a correction coefficient + 7 minutes is proposed;  for cylinders of 7 litres, this difference is significant (8 minutes) which is 23% of the error, respectively, the introduction of a correction coefficient + 8 minutes is proposed for the base formula. Additionally is proposing, for SCBA of double-cylinder design, such as Drager PSS-5000 in the proposed formulas additionally average working time of the firefighters in the SCBA multiply by two. Thus, based on the above, in the practical calculations for the determination of the average time of operation of firefighters in a gasified and smoked environment, during using SCBA with cylinders of 6.8 and 7 litres, or a doublecylinder construction, it is proposed to apply correction coefficient to the base formula. However, for an SCBA with a cylinder capacity of 6 litres leave the formula unchanged. The introduction of the correction factors in the basic formula will enable firefighters units safely carry out intelligence during fire extinguishing, elimination of emergencies and their consequences, saving people and evacuation of material values from gassed and smoky premises.