Ensuring safe evacuation of people from nightclubs

. The paper considers the problems of standardisation of evacuation routes and exits in nightclub buildings. The absence of regularities of people's movement in such buildings in the normative and research literature does not make it possible to estimate adequately the projected and existing planning decisions from the point of view of providing the safe evacuation of people, but also the value of individual fire risk. The analysis of fires has shown that the main cause of loss of life in a nightclub fire is untimely evacuation due to the accumulation of human traffic in front of the building exits. In order to determine the parameters of the flow of people, there were conducted preliminary field observations in nightclub buildings. Statistical analysis of the data obtained made it possible to establish the dependence of the movement of people up and down the stairs, horizontal path and through the doorway. The results of modeling of people evacuation have shown significant differences between the data presented in the methodology of assessment of fire risk and the data obtained in the research. The data obtained allow a reliable assessment of the criteria of safe evacuation of people in the design and operation of nightclubs, as well as the calculation of individual fire risk.


Introduction
The safety of the building occupants in the event of a fire is determined by criteria to ensure timely and unimpeded evacuation (according to Federal Law "Technical Regulations on Fire Safety Requirements" of 22.07.2008N 123-FZ).To assess these criteria, different models of human movement and the development of fire hazards are used (according to Order No. 382 of the Ministry of Emergency Situations of Russia dated June 30, 2009 "On approval of the methodology for determining the estimated fire risk in buildings, structures and constructions of various classes of functional fire hazard" with amendments approved by Order No. 632 of the Ministry of Emergency Situations of Russia dated 02.12.2015).The choice of the human flow model and the list of input data determine the validity of the results and their adequacy to the real picture of the human movement process.When designing and operating a nightclub building, it is of primary importance to ensure that there is unobstructed flow of people along escape routes and through escape exits.At the same time, the layout solutions of the communication paths determine the functional processes in the building [1], one of which is the human traffic process, and their parameters (speed, density and intensity) determine the geometric dimensions of the evacuation routes in case of fire.At present, current regulations [2,3] define the dimensions of evacuation routes according to the parameters of healthy people without physical and psychological limitations.At the same time, the existing requirements do not take into account the psychophysiological features of behaviour and movement of people in nightclubs.There are no scientifically based data in the scientific and regulatory literature (SNiP 2.08-02-89*.Public buildings, Manual to SNiP 2.08-02-89* "Design of Clubs") [4][5][6][7][8][9][10][11][12][13][14][15], which does not allow reliable determination of the optimum dimensions of escape routes and exits.
Non-compliance with fire safety requirements in establishments designed for catering and people's leisure time at night has caused over 1000 fatalities in the last 20 years alone.Table 1 shows statistics on fires in nightclubs both in Russia and abroad with the number of people killed and injured.The high number of deaths and casualties is due to the failure to meet the evacuation criteria for safe evacuation.Visitors do not have time to leave the premises before the critical values of fire hazards are reached, usually forming a crush for a long time due to the insufficient capacity of evacuation exits.
Standardisation of the safety evacuation criteria starts with the classification of protection facilities according to their function.However, in the case of nightclubs, there is no unambiguous classification.On the one hand, clubs are allocated to functional fire hazard class F 2.1 (clubs), but there is another opinion, class F 2.2 (dance floors).
Moreover, the existing classification (according to Federal Law "Technical Regulations on Fire Safety Requirements" of 22.07.2008N 123-FZ) does not reflect functional features of modern nightclubs, which makes it impossible to reliably evaluate the adopted planning solutions from the point of view of providing safe evacuation of people.A characteristic feature of modern nightclubs is an irregular number of visitors.Whereas the seating area may imply a certain number of visitors, the dance floor implies a chaotic distribution of a large number of people.
In this case, the area occupied by each person is extremely small and there is a risk of an overcrowding situation that does not meet the normative design figure.Hence the inability of existing space planning solutions (i.e., escape routes and exits) to meet the criteria for safe evacuation.
BC 118 [2] suggests that the capacity of auditoriums in clubs should be determined on the basis of estimated floor space per seat.Due to the fact that the main functional contingent of the buildings under consideration is on the dance floor, the application of the requirement [2] in the design of evacuation exits is illegitimate.
The width of exit from the halls is determined depending on the volume of space, the degree of fire resistance of the building, and the number of people per 1 m of exit width [3].There should be at least two emergency exits in halls with capacity of 50 people or more, and their width should be at least 1.2 m.According to the requirements of para.7.4.1 BC 1 [3] to calculate the escape routes and escape exit capacity of dance halls is taken at a rate of 1.35 m2 area of the hall area for 1 person.
However, the above requirements do not take into account the psychophysical characteristics of behaviour and movement of people under the influence of alcohol.

Materials and methods
In order to establish the calculated parameters for the movement of people in nightclubs, field observations of the movement of people up and down stairs and through doorways were carried out according to the methodology [15].The indicator of the normative area per person was also investigated.
Video footage was taken during the entire opening hours of the nightclub, namely from 23:00 to 04:00.As a result of the experiment, the number of visitors coming and going depending on the time interval was recorded to determine the maximum number of visitors at a certain time interval t.The values obtained are shown in Table 2.The estimated floor space per person in the nightclub is based on the ratio of the main lounge area Sl to a maximum number of people Nmax, at time t in the clubhouse.The calculated floor space per person is 0.55 m2/ppl.
In order to establish the relationship between speed and density of the flow of people up and down the staircases, video footage was taken continuously throughout the opening hours of the nightclub.The analysis of the video recordings revealed the velocities of free movement of people, which requires additional research to be conducted.

Statistical processing of the obtained results on the human flow rate
The empirical data obtained from the field observations on the free-flow velocity of people were processed using mathematical statistics methods with the SPSS Statistics software.The results of the statistical processing are presented in Table 3 for the downward movement of the stairs and in Table 4 for the upward movement of the people on the stairs.Histograms of the distribution of the people free flow velocity up and down the stairs are shown in Fig. 1, 2.

Results
Using the resulting free motion velocities V0 Taking into account the psycho-physiological state of visitors in the nightclub, the speed and traffic density dependencies for the upstairs and downstairs have been established, using the previously established coefficients a and Do [16,17] (Fig. 3-6).On the basis of the previously established patterns of movement of people along different sections of the path by V.V. Kholschetnikov.Holshchevnikov, to establish the dependence of the movement of people along the horizontal part of the path and through the doorway, we assumed that the speed of free movement down the stairs corresponds to the speed of free movement along the horizontal part of the path and through the openings [16,17].As a result, preliminary graphs of the dependence of speed and intensity of movement on the density of human flow were constructed, presented in Fig. 7-9.The results of in-situ observations showed a significant difference between the free-flow velocities presented in methodology (according to Order No. 382 of the Ministry of Emergency Situations of Russia dated June 30, 2009 "On approval of the methodology for determining the estimated fire risk in buildings, structures and constructions of various classes of functional fire hazard" with amendments approved by Order No. 632 of the Ministry of Emergency Situations of Russia dated 02.12.2015) and the real data, Table 5.To comparatively assess the impact of the parameters of human traffic presented in the methodology (according to Order No.The results of the simulation of the human traffic with regard to the obtained data are given in Table 6.Comparing the results obtained showed that the difference between the values of calculated evacuation times, taking into account the data presented in the Methodology and the results of in-situ observations, was -for evacuations involving a section of track with stairs upwards -438.4 s, which is a difference in the results of 71%.
-For evacuations involving the down stairway section of track -382.1 s, which is a difference in results of 74%.

Conclusion
The results obtained show the necessity of continuing research in the field of people movement in different parts of the path in nightclubs, taking into account the psychophysical state of people, to establish reliable parameters of human traffic, determining the geometric parameters of evacuation routes.
The initial results formed at this stage are a theoretical basis for modelling the evacuation of people and for updating the current regulatory requirements in the field of standardisation of evacuation routes and exits in nightclubs.

Fig. 1 .Fig. 2 .
Fig. 1.Histogram of the people free flow rate distribution up the stairs.

Fig. 4 .
Fig. 4. Dependence of downstairs traffic intensity on the density of human traffic.

Fig. 6 .
Fig. 6.Dependence of the upward movement rate of the stairs on the density of human traffic.

Fig. 7 .
Fig. 7. Dependence of horizontal track velocity on the density of human traffic.

Fig. 8 .
Fig. 8. Dependence of horizontal track traffic intensity on human traffic density.

Fig. 9 .
Fig. 9. Dependence of traffic volume through exits on human traffic density.
382 of the Ministry of Emergency Situations of Russia dated June 30, 2009 "On approval of the methodology for determining the estimated fire risk in buildings, structures and constructions of various classes of functional fire hazard" with amendments approved by Order No. 632 of the Ministry of Emergency Situations of Russia dated 02.12.2015) and obtained from in situ observations on the estimated evacuation time, the modelling was carried out in the Pathfinder software, implementing an individual-flow model of human traffic, Fig. 10.As a design situation, scenarios of people movement up and down stairs were considered, taking into account the layout of the nightclub, where full-scale observations were made.The free movement velocity of the people Vo for the stairs upward was taken as 40 m/min, for the horizontal route, the stairs downward and the doorway as 30 m/min.The coefficients a and Dо have been assumed according to the methodology (according to Order No. 382 of the Ministry of Emergency Situations of Russia dated June 30, 2009 "On approval of the methodology for determining the estimated fire risk in buildings, structures and constructions of various classes of functional fire hazard" with amendments approved by Order No. 632 of the Ministry of Emergency Situations of Russia dated 02.12.2015).The width of the staircase is 1.2 m, and the width of the doorway 1.2 m.

Table 1 .
Statistics on fires in night cubes.

Table 2 .
Number of visitors per time interval.

Table 3 .
Processing the results of the observations for downstairs movement.

Table 4 .
Processing the results of the observations for the upward movement of the stairs.