1. Introduction
After traffic accidents, burn injuries are the second leading cause of death among children in Iran. Children are particularly vulnerable to burn injuries due to their limited understanding of dangerous situations and their difficulty in reacting quickly and appropriately. Furthermore, their tendency to panic can complicate emergency management, making it challenging to ensure their safety during crises [1,2].
In Iran, children under the age of 12 attend elementary schools, where they typically spend about five hours each day; therefore, ensuring the safety of these educational buildings is essential. However, reports indicate that a significant number of fires occur in elementary schools, accounting for 65.5% of all fire incidents [1]. In recent years, Iran has experienced several devastating school fires. Between 1996 and 2019, the country recorded fourteen major school fires that resulted in the deaths of 30 students and one teacher, as well as serious injuries and disabilities affecting 63 students and 15 teachers [1]. Tragic incidents of this nature have also occurred in various countries, including Kenya, South Korea, China, Saudi Arabia, India, and Russia, leading to the loss of over a hundred children and teenagers’ lives and causing significant injuries [1,3].
In fire incidents, despite the implementation of various medical and surgical interventions and substantial financial investments, serious burn injuries in child victims often result in long-term complications. Additionally, psychological consequences such as anxiety, depression, and post-traumatic stress disorder (PTSD) can persist for years [1,3].
One of the primary responsibilities of the Ministries of Education and Health (MoHME) is to develop and implement a comprehensive plan to ensure safe conditions in schools [1].
Therefore, in light of the costs and economic consequences, implementing safety measures—particularly emergency response planning and enhancing school fire safety policies—is of utmost importance [4].
A critical aspect of designing fire protection systems is ensuring the safe evacuation of occupants, which is especially important in gathering centers such as schools [1]. Therefore, researching students’ evacuation processes and behaviors during a fire is essential [1,3,4].
The term “evacuation” refers to the safest, shortest, and fastest method of moving people, animals, materials, and property from a hazardous location to a secure one. The appropriate evacuation strategy may vary depending on the reason for the evacuation [5].
In this context, several studies have been conducted to identify and evaluate the factors influencing the evacuation processes of various student populations. One study focused on students with intellectual disabilities and found that the floor level from which children were evacuated significantly affected their evacuation times. Children on higher floors exhibited longer reaction and pre-movement times, as well as slower vertical and horizontal movement speeds compared to those on lower levels [6]. Additionally, other studies have shown that when certain escape routes are blocked by fire, evacuees often redirect themselves to the nearest floors and stairwells, complicating the evacuation process [4].
Human behavior during emergencies is complex, often influenced by a panicked mental state, unusual reactions to flames and smoke, or unfamiliarity with the building. Therefore, using software that can predict evacuation processes through mathematical modeling is highly beneficial [7]. Pathfinder software has been utilized to simulate emergency evacuations in both adult educational centers and schools. One of its primary applications is comparing different evacuation routes to identify the optimal path during a fire crisis [8,9,10,11,12].
Pathfinder’s user-friendly interface allows researchers to obtain insightful quantitative and qualitative results regarding evacuation route analysis and occupant movement in fire emergencies [13,14]. The software offers both two-dimensional (2D) and three-dimensional (3D) visualizations of simulation time histories, enabling the definition of various scenarios and facilitating the integration of results into SMART building management systems [15].
These features contribute to Pathfinder’s popularity as a tool for evacuation modeling among researchers [16,17,18,19].
Therefore, this study aimed to simulate fire emergency evacuations in an elementary school using Pathfinder software, concentrating on a large number of students (occupants) and identifying the architectural characteristics that influence evacuation effectiveness.
2. Materials and Methods
2.1. Characteristics of the Study
This case study was conducted in Qazvin City, Iran, to simulate the emergency evacuation of students and staff in an elementary school and to identify the geometric factors that influence total evacuation time. The study utilized Pathfinder version v2021.3.0901 x64 software to analyze the evacuation conditions for the school’s occupants, considering factors such as evacuation density on each floor, traffic conditions along various routes, and the volume of traffic at the exit doors. Additionally, two-dimensional (2D) and three-dimensional (3D) maps of the building were created using Revit 2018 software.
2.2. General Framework of the Study
Before data collection began, necessary permits were obtained from the General Office of Education of Qazvin Province and the relevant district authorities. In this research, general framework of the study was conducted according to Figure 1.
The first step involved reviewing previous studies that assessed student behavior and emergency exit situations in elementary schools during fires.
In the second step, an evaluation of the building was conducted to identify the presence of combustible and non-combustible materials in the rooms and school spaces. Through the synthesis and analysis of data from these investigative and evaluative methodologies, areas of elevated risk were identified, particularly in the office pantry and laboratory facilities. These locations demonstrated a statistically significant increase in the probability of fire occurrence compared to other areas within the premises.
Due to the inactivity of the laboratory and insufficient information regarding it, the office pantry—located at the eastern end of the ground floor—was selected as the fire scenario location. This choice was influenced by the improper storage of nylon bags, one of the combustible materials found in the office pantry, which were located near the gas cooker (a potential fire source). Thus, the scenario of burning nylon bags was considered for the simulation.
Following this, the conditions of the school building, including fire alarm and extinguishing equipment, were analyzed, and the burning reaction of nylon was defined in Pyrosim v2021.3.0901 x64 software to simulate the desired fire dynamics and obtain the Available Safe Egress Time (ASET).
Subsequently, data to simulate the emergency evacuation of school occupants (students and staff) were collected. This data were categorized into two groups: the geometrical characteristics of the building and the demographic information about the occupants.
To collect data on the dimensions of the rooms and the geometric characteristics of the school building, field observations were conducted within the school environment. Measurements were taken for the areas of classrooms, corridors, and stairways, including the dimensions of classrooms, office spaces, the health room, the prayer room, and the laboratory. The widths of all corridors—especially the exit corridors—and the depth and width of the stairs were also assessed. The dimensions of the doors were recorded, and all results were entered into specially prepared forms.
Additionally, interviews and anthropometric measurements were used to gather data on the school occupants, including their age, gender, height, shoulder width, body width, physical health status (indicating whether they required physical assistance), and their experience participating in evacuation drills. The school population comprised 489 students and 33 staff members, totaling 522 individuals.
The video of the simulated evacuation produced by the software was subsequently analyzed. During this analysis, the capabilities of Pathfinder software were utilized to observe various metrics, including the amount of traffic behind the exit doors, evacuation density on each floor, and the flow of evacuees along different routes.
Effective geometric factors in the emergency evacuation scenario, such as the widths of exit corridors and doors—particularly the main entrance and exit door—were compared against relevant internal standards to assess their influence on total evacuation time. All identified effective factors were adjusted simultaneously, and the simulation was repeated to evaluate the overall impact of these modifications.
Furthermore, to assess the effect of reducing the school population, the number of students was decreased in accordance with the internal standards for Iranian educational building design, and another simulation was conducted based on this adjusted population.
2.3. Building Description and Observations
Introduction to the Selected Schools
The selected elementary school is located in Qazvin City and has a total area of 4683.6 m2. The school features a regular rectangular geometric shape and consists of two floors.
The ground floor includes two management offices, a health room, a pantry, a staff room, a training room, and eight classrooms. The first floor contains a laboratory, a prayer room, an office room, a consultation room, and eight additional classrooms.
The ground floor features one staircase, while the first floor has two staircases. Through field observations and direct measurements, the dimensions of various spaces—including classrooms, management offices, the health room, counseling room, education room, staff room, laboratory, pantry, and prayer room—were recorded in the appropriate worksheets (see Table 1).
Additionally, measurements were taken for the widths of all corridors, particularly the exit corridors; the height of the handrails; the depth and width of the staircase steps; the height of the stair treads; the dimensions of doors, including the entrance and exit doors of the school building; the height of the front of the staircases; and the dimensions of classroom doors.
Each classroom is equipped with tables and chairs, accommodating an average of approximately 30 students. Plan view of the ground floor and first floor were showed in Figure 2 and Figure 3. Subsequently, 3D models of the school building complex were developed using Revit 2018 software (Figure 4). The IFC output was then obtained and imported into Pathfinder 2021 software for further analysis.
2.4. Personnel Parameters
The school had a total of 522 occupants, comprising 33 teachers and administrative staff, as well as 489 students across 16 classes, which included five first-grade classes, six second-grade classes, and five third-grade classes. To create a profile of the school occupants (students and staff) in Pathfinder software, the occupants were first categorized, and then students from each class and staff members were examined separately.
Demographic and anthropometric data were collected for all 522 individuals, including height, shoulder width, body width, age, sex, physical health status (indicating whether they needed physical support), and experience participating in training drills. The summarized characterization of the occupants in the school building is presented in Table 2. Subsequently, the mean, standard deviation, and maximum and minimum values were calculated.
Modeling of school occupants was performed by constructing profiles based on sex (male/female) and health status (healthy/needing assistance). Ultimately, 17 profiles were created using Pathfinder software.
2.5. Details and Procedures for Evacuation
2.5.1. Scenario Types
In the initial research, the school pantry was designated as the starting point for the hypothetical fire scenario. Located at the eastern end of the ground floor, between two classrooms, the pantry presents a heightened risk for fire incidents due to the storage of flammable materials, such as nylon bags, and the presence of cooking oils near gas appliances. Consequently, the pantry was ultimately selected for the fire scenario.
Given the improper storage of nylon bags next to the gas cooker, the scenario of burning nylon bags in the school’s pantry was considered. Pyrosim software was utilized to calculate the Available Safe Egress Time (ASET), which refers to the time at which the safety exit is available. In contrast, the Required Safe Egress Time (RSET) is the time required to reach the safety exit once it has been activated [20]. RSET is calculated as the sum of evacuation delay times obtained from simulations, beginning at the moment the fire detectors are activated in the simulations. ASET is derived from the initial fire simulation results for selected fire scenarios using the Fire Dynamics Simulator (FDS) and the Consolidated Model of Fire Growth and Smoke Transport (CFAST). RSET is calculated using Pathfinder software [21]. ASET greater than RSET (ASET > RSET) is considered safer than when ASET is less than RSET (ASET < RSET) [22].
In this study, Pyrosim software was employed to calculate the ASET. Within this software, the burning reaction of nylon bags in the school pantry was defined according to the fire scenario, and the simulation of fire development was conducted for a period of 380 s. Ultimately, the available Safe Egress Time was determined based on the results related to changes in visibility, temperature, and carbon monoxide concentration throughout the simulation period.
Also, the Required Safe Egress Time (RSET) is calculated using the following relationship [12]:
Alarm Time (Talarm) + Response Time (Tpre) + Evacuation Time (Tmove)
In this study, given the conditions of the school (which lacks any fire alarm and extinguishing systems), the alarm time is estimated at 60 s, based on similar studies [12]. The response time for students is also set at 60 s due to their lack of experience in handling unexpected incidents. Additionally, a factor of 1.5 was applied to the emergency evacuation time calculated using Pathfinder software. Therefore, the RSET is calculated using the following formula:
Alarm Time (60 s) + Response Time (60 s) + 1.5 ∗ Evacuation Time
The school building consists of two floors connected by a staircase. It features an entrance and exit door with a width of 1.8 m, located 8.4 m from the base of the staircase on the ground floor, positioned directly in front of it. Based on observations of students’ exit behaviors, this entrance and exit door serves as the primary evacuation route for all occupants, including both students and staff.
Considering the behavioral characteristics of the school population, which includes both children and teachers, the third scenario was deemed the most appropriate among the three potential evacuation strategies:
Scenario 1: “Go to Any Exit!” (Default Scenario, Current Fire Emergency Evacuation Plan)
Scenario 2: “Familiar Routes” (Main Entries of the School)
Scenario 3: “Follow the Teacher!” (Children’s Preference)
This selection is based on the understanding that children are more likely to follow their teachers during emergencies [23] (see Figure 5).
2.5.2. Description of Scenario
In this simulation, a fire accident was modeled in the pantry located at the eastern end of the ground floor of the school building, which has an area of 6.5 m2 and a single exit with a door width of 90 cm. The fire was assumed to have broken out at 8:30 a.m., when all students and staff were present in the school. At the time, two workers were occupying the pantry. The total number of people on the ground floor was 262.
In this study, scenario 1 was chosen to simulate the exit of students from the school building. The conditions of the evacuation scenario are summarized in Table 3, while the layout of the floors and the location of the initial fire are illustrated in Figure 5 and Figure 6.
The capacities of the corridors and emergency exit routes, as well as the suitability of the door dimensions in relation to the volume of occupants, were evaluated. In the simulation conducted using Pathfinder software, the evacuation density of floors and rooms per unit of time, along with the number and types of escape routes taken by individuals, were considered. Additionally, the utilization of these routes, the traffic volume behind the exit doors, and the delay and travel times were calculated. The total travel time, which represents the complete time taken to evacuate the building, was also determined.
According to previous research on physical emergency evacuation maneuvers and simulations conducted using Pathfinder software in an elementary school in Iran with 345 students, the estimated movement speeds were between 1.0 and 1.1 m/s for students and 1.1 and 1.2 m/s for staff [13]. Similar to the school in our study, the referenced school also lacked both active and passive fire protection systems, as well as an emergency response plan.
2.6. Introduction of the Pathfinder and Details of the Evacuation Simulation in the School Building
Pathfinder is a commercial evacuation simulation software developed by Thunderhead Engineering, designed to provide a graphical user interface for modeling evacuation processes. It utilizes parameters such as the number of occupants, walking speed, and evacuation distance to simulate various scenarios [24].
Widely used in evacuation simulations and disaster prevention, Pathfinder is based on human behavioral factors, including passenger movement and individual characteristics. The software presents simulation results in both qualitative forms (2D and 3D graphics) and quantitative forms (such as evacuation times, the number of individuals evacuated, and population density) [16,25].
In this study, the geometry of the school was categorized into three main types—doors, rooms, and stairs—using Pathfinder software. The main steps of the simulation were as follows:
Geometry Creation: The geometry of the selected school, including rooms, doors, stairs, and corridors, was created and prepared for simulation. These data were imported from Autodesk Revit 2018 software.
Room Arrangements: Arrangements were organized within the rooms.
Access Configuration: Connections between corridors and stairs were established, and doors were added.
Passenger Addition: Occupants were added to the simulation.
Behavioral Modeling: A three-dimensional model of behavioral aspects for the residents was defined.
Simulation Implementation: The simulation was executed.
Post-Processing: Quantitative data visualization and analysis were performed.
2.7. Identifying Geometrical Factors Affecting the Emergency Evacuation Time of School Occupants
Two methods were employed to identify the geometrical factors that influence the emergency evacuation time of students and staff in the school:
○. Simulation Analysis: The results of the emergency evacuation simulation for the school’s occupants were analyzed and interpreted using the features in Pathfinder software. This allowed for the observation of evacuation density on each floor, the volume of traffic behind the doors—particularly the school exit door—and the flow of traffic along the exit routes.
○. Comparison of Effective Geometric Factors in Emergency Escape: This method involves evaluating factors such as door width and hallway width against relevant internal standards, utilizing two specific regulations [26,27]. The items identified as inconsistent with these standards and deemed influential are listed in Table 4.
Finally, based on the two methods mentioned above, four key factors were identified as effective in reducing evacuation time:
○. The direction in which the doors open in classrooms and staff rooms
○. The width of the school exit door
○. The width of the exit corridors on each floor
○. The area of the classrooms
Details of the changes made to each identified factor are provided in Table 5. Following these adjustments, the simulation of the school emergency evacuation process for the occupants was repeated.
2.8. Simulation Based on Reducing the Number of School Students
The design criteria for educational buildings, as outlined by the Organization for Development, Renovation and Equipping of Schools (DRES) of I.R. Iran (2016), specify that the classroom area per student in urban elementary schools should average 1.75 m2, with a maximum capacity of 30 students [27]. This guideline is further supported by national building regulations concerning fire protection for buildings [26].
To ensure that the classroom space is proportional to the number of students, we reduced the number of students in each class to 20 and subsequently repeated the simulation based on this adjustment.
3. Results
3.1. Results of the ASET Calculation
The simulation results of the fire dynamics in Pyrosim software indicated that within 180 s of the fire starting, the conditions in the school worsened significantly; visibility in the ground floor corridor dropped to less than 5 m and smoke from the fire spread throughout the entire floor, indicating a high concentration of smoke. Additionally, the ambient temperature at the location of the emergency exit door exceeded 100 °C within this same timeframe. Therefore, the findings suggest that all school occupants, especially students, must evacuate the building before this critical time. As a result, the Available Safe Egress Time (ASET) is determined to be 180 s (see Figure 7, Figure 8, Figure 9, Figure 10 and Figure 11).
3.2. Results of Emergency Evacuation Simulation
The total simulated evacuation time obtained by running the software is 386 s (Figure 12).
Based on the total evacuation time, the Required Safe Egress Time (RSET) was calculated to be approximately 700 s, which is significantly greater than the Available Safe Egress Time (ASET) of 180 s. This disparity highlights the adverse conditions for emergency evacuation in the studied school.
60 s + 60 s + (1.5 ∗ 386) = 699 s
A time-dependent graph was created to illustrate the number of occupants in a room over time (Figure 13). This graph divides the entire evacuation process into three segments of 100 s each. It shows that 100, 200, and 300 s from the start of the evacuation, a total of 180, 379, and 457 occupants (students and teachers) were evacuated, respectively. In other words, 1.66, 3.33, and 5 min from the start of the evacuation, approximately 342 occupants (equivalent to 65% of the total) remained in the school, along with 143 and 65 occupants who had not yet evacuated. The change in passenger flow rate over time is depicted in Figure 14.
According to Figure 13, from 16 s to 205 s, the flow rate of evacuees increased uniformly, resulting in 382 occupants successfully exiting the building at an average flow rate of approximately 2.05 persons per second (Pers/s). However, from 205 s until the end of the evacuation (385.5 s), the flow rate significantly decreased to 0.75 Pers/s. This indicates that despite a substantial reduction in the number of remaining occupants—down to 134 out of 522 at 205 s—the evacuation process slowed considerably during the final stages. This happened because the remaining students on the first floor faced heavy staircase traffic, slowing their speed to the ground floor.
The relationship between the number of evacuees and the change in passenger flow rate over time is illustrated in Figure 14. The data indicate that the evacuation process in the school building is slow; occupants begin moving 16 s after evacuation starts, and the flow rate of evacuees remains low, at less than one person per second (Pers/s).
Figure 15 presents the flow rates of evacuating occupants in the corridors between the ground floor and the first floor, illustrated in Figure 15A–E. The ground floor corridors are shown on the left, while the first floor is on the right.
The layouts from Figure 15A–E correspond to evacuation times of 29.6, 61.6, 198.4, 204.9, and 342.1 s, respectively. The layouts indicate that at 29.6 s, traffic behind the exit door on both the ground and first floors increased significantly. The evacuation flow rate in the exit corridor exceeded three people per square meter, with these high-density areas marked in red. Low-density populations are depicted in blue, while the color spectrum transitions from blue to yellow and then red, indicating increasing density.
High-density evacuation on the ground-floor and the first-floor staircases persists until 204.9 s. By 342.1 s, occupants are evacuating from the first floor and passing through the ground-floor staircase at a high density.
3.3. Results of the Impact of Geometrical Changes on the Emergency Evacuation Process
The results of the simulation on the impact of geometric changes on the emergency evacuation process are summarized in Table 6. Overall, implementing all proposed changes reduced the total evacuation time by 21.2 s (see Figure 16 and Figure 17). Notably, the most substantial decrease in evacuation time—17.5 s—was achieved by increasing the area of the classrooms. In contrast, altering the width of the main staircase had a minimal impact on evacuation times. Also, the geometrical changes made to the parameters of the school building for subsequent simulations are shown in Table 5.
3.3.1. Results of Changing the Opening Direction of the Doors of All Classrooms Towards the Exit
As a result of this change, the total evacuation time was minimally reduced by approximately three seconds, as illustrated in Figure 18. Notably, at the 150 s mark of the emergency evacuation, 250 occupants had yet to evacuate and remained inside the school.
3.3.2. Results of Changing the Width of the Entrance and Exit Door on the Ground Floor
As shown in Figure 19, increasing the width of the entrance and exit door on the ground floor resulted in a minimal reduction of approximately 4.2 s in the total evacuation time of the school.
In this case, although the overall duration of the emergency evacuation did not significantly decrease, doubling the width of the entrance and exit doors resulted in an increased evacuation speed. By the 120 s mark, the improved speed facilitated the successful evacuation of 350 occupants by the 150 s mark, leaving 172 occupants still inside. In contrast, under the previous conditions resulting from the initial changes, only 272 occupants had evacuated by the 150 s mark. This indicates that this modification allowed for the evacuation of 78 more individuals during the first 150 s compared to the initial scenario.
3.3.3. Results of the Increase in the Width of the Exit Corridors on the Ground and First Floors
The width of the exit corridors was increased by one meter in this case. The total emergency evacuation time remained unchanged (see Figure 20). With this modification, 281 occupants were evacuated within the first 150 s, leaving 241 occupants still inside.
3.3.4. Results of Increasing the Area of Classrooms to 45 m2
Increasing the area of the classrooms resulted in a reduction in evacuation time by 17.5 s. This expansion of the school’s space, along with a decrease in classroom population density, accelerated the emergency evacuation process (see Figure 21). With this adjustment, 275 occupants were evacuated within the first 150 s, leaving 247 occupants still inside.
3.4. Simulation Results Based on Reducing the Number of School Occupants
The simulation results indicated that reducing the number of students to 353 occupants decreased the total evacuation time by 128 s, allowing for complete evacuation in just 257.5 s. As shown in Figure 22, the rate of evacuation speed increased dramatically during the first 150 s, with many occupants reaching the entrance and exit doors within the first minute (see Figure 23). By the 150 s mark, only 77 occupants remained in the school (Figure 22), while 276 had successfully evacuated (Figure 24). However, after this point, increased population density in the staircases on the first and ground floors created heavy traffic, which slowed down the evacuation speed. The remaining 77 occupants managed to exit the school within an additional 107 s (Figure 24). Additionally, the Required Safe Evacuation Time (RSET) in this scenario reached 505 s, which, although reduced by approximately 200 s compared to the first mode, still exceeded the ASET.
4. Discussion
Fire disasters can easily occur in schools due to their architectural properties and the behavioral characteristics of students [14]. Children represent a particularly vulnerable population that typically requires assistance during the evacuation process. The evacuation process for children differs from that of adults due to age-related factors and behavioral conditions [28], as many evacuation parameters are age-dependent [29]. Therefore, there is an urgent need to implement emergency exit simulations in schools, especially in elementary and densely populated institutions that are more susceptible to such risks. Effective monitoring and prevention of fire disasters in schools can significantly reduce both economic and social damages [14].
This research highlights the benefits of using fire evacuation simulation tools and investigates the effects of population density and structural changes in human mass centers, such as schools. The primary objective was to examine the evacuation times of occupants during fire incidents in a school environment and to analyze how modifications to exit routes can enhance safety and facilitate successful evacuations.
The evaluation of the current situation revealed that the evacuation time for occupants exceeded 6 min (386 s) (see Figure 12). To identify the underlying causes of this extended evacuation time, various structural characteristics were simulated, including the following:
The opening direction of classroom and staff room doors.
The width of the entrance and exit doors on the ground floor.
The width of exit corridors on each floor.
The area of classrooms.
The overall population density.
When classrooms are closed, students often crowd behind the doors, making it necessary to open them for evacuation. Previous studies have confirmed that aligning the direction of door openings with the direction of escape significantly increases evacuation speed. Coordinating the flow of evacuees with the direction of door openings can greatly enhance evacuation efficiency [30]. Therefore, the design of school buildings and the mechanisms for opening and closing doors are crucial considerations [31].
In our study, the doors of the classrooms opened inward, which led to congestion behind the doors during emergency exits, hindering quick evacuation. Our results indicated that changing the opening direction of all classroom doors reduced the evacuation time by 3 s. While this reduction may seem minimal, it can have a cumulative effect when combined with other modifications.
One of the most common challenges during emergency evacuations is the accumulation of occupants behind exit doors. Overcrowding can complicate evacuation efforts, potentially leading to secondary disasters and injuries from crushing. During a fire, the effective width of escape and exit doors plays a crucial role in reducing panic among children and improving the organization of occupants during evacuation [32]. In escape routes, both the width of the doors and the composition of the population significantly affect density conditions [33,34].
In this study, we examined the impact of increasing the width of the exit door as a probabilistic factor in reducing evacuation time. The results indicated that widening the exit door from 1.8 to 3.6 m reduced the total evacuation time by 4.2 s. While this reduction may seem insignificant on its own, it becomes noteworthy when compared to a secondary or high school that utilized an exit door with a width of just one meter. In that scenario, 615 students and staff could achieve better relative safety [35].
Another study conducted in the Netherlands examined the effects of evacuation door width and population composition on the capacity of evacuation doors among students with an average population density. The findings revealed that the widest door opening, measuring 275 cm, resulted in the lowest stress levels for evacuating students, reduced crowd density, and increased evacuation speed. The study tested door opening widths that varied between 50 cm and 275 cm [33].
Considering the speed of vertical movement on the stairs, factors such as density and flow rate in the escape exits can psychologically impact children’s performance during emergency evacuations [34]. Therefore, in our study, we simulated an increase in the width of the exit corridors on both the ground floor and the first floor as a potentially effective geometric modification.
Our results indicated that increasing the width of the exit corridors did not lead to a noticeable change in the total emergency evacuation time. The corridors and stairs of the building play a crucial role in the successful evacuation and rescue of individuals during a crisis [35]. While wider corridors generally facilitate an increase in evacuation flow speed [36], this particular study did not yield a successful outcome with the modifications implemented [36].
Increasing the area of the classroom was identified as one of the significant geometric changes within the school. This modification resulted in a reduction of total evacuation time by 17.2 s, demonstrating greater optimization compared to other changes. Previous studies have primarily focused on factors such as flow through doors, walking speed, density [28,33,34,37], distance, visibility, selection of exit doors, and the impact of classroom layout on emergency evacuation times [6,28,34,35,36]. However, no studies have specifically examined the effect of classroom area on evacuation time.
This study demonstrated that combining all geometric changes in the building resulted in a significant improvement, reducing the total evacuation time by 21.2 s compared to the single-change mode (see Table 6). Therefore, employing multi-factor combined approaches in building design yields better evacuation performance than designs controlled by single factors [38].
In this research, a simulation was conducted to examine the effects of reducing the number of school occupants as a non-geometric change. The results indicated that lowering the number of occupants from 522 to 353 could decrease the total evacuation time by 128 s. Thus, the primary factor contributing to the prolonged evacuation time is the large number of occupants in the school. Previous studies have shown that an increase in the number of people can lead to overcrowding in stairwells and behind doors, creating bottlenecks that prolong evacuation time [5,6,29]. A high student population significantly extends evacuation duration. While human flow in school buildings under normal conditions varies by the age of the children, increased density consistently leads to a decrease in travel speed across all age categories [5,28].
According to the results of this study, the conditions of the school building (which lacked automatic fire detection and extinguishing systems) and the type of fire reaction considered in the fire scenario indicated that the Available Safe Egress Time (ASET) was approximately 180 s. In contrast, simulation results of the emergency evacuation showed a total evacuation time of 386 s. Given the conditions of the school building and the inexperience of the students (due to the absence of emergency evacuation drills), the Required Safe Evacuation Time (RSET) was calculated to be around 700 s. Therefore, under the current conditions of the studied school, the RSET exceeds the ASET by more than 8 min for a population of 522 occupants.
Even in the last simulation, which involved reducing the number of students and resulted in a 128 s reduction in total evacuation time, the RSET (505 s) still far exceeded the ASET. The significant disparity is primarily due to the inclusion of alarm time (60 s) and response time (60 s) in the RSET calculation. Thus, implementing fire detection and extinguishing equipment [12] and conducting regular emergency evacuation exercises to increase student readiness [13] are crucial to reducing the RSET. Furthermore, if additional safety measures and control strategies are considered in the studied school—such as reducing alarm and response times and improving student evacuation conditions—the RSET can be significantly decreased, thereby facilitating safer emergency evacuations.
Limitations and Recommendations
Due to the study conditions, it was not possible to conduct evacuation drills with students and staff to validate the simulation results effectively. Therefore, validation was achieved by comparing the model’s predictions to historical data from similar incidents.
Additionally, this study focuses on a single case study. While the selected school exemplifies many common challenges, it would be beneficial to compare it with other building types and occupant demographics to draw broader conclusions. We recommend that future studies examine schools with contrasting layouts or diverse occupant populations to enhance the generalizability of the findings.
5. Conclusions
This research highlights the benefits of utilizing fire evacuation simulation tools and examines the impact of population density and geometric changes in human mass centers such as schools. The evacuation simulation revealed that the evacuation process took over six minutes, indicating a need for improvement. To investigate the causes of this prolonged evacuation time, the effects of modifying four geometric characteristics and the number of occupants were simulated.
The most effective geometric modifications for reducing emergency evacuation time included increasing the classroom area, widening the entrance and exit doors on the ground floor, and changing the opening direction of all classroom doors to swing outward. Notably, combining all these geometric changes resulted in a total evacuation time reduction of 21.2 s compared to implementing individual changes.
Additionally, a simulation was conducted to evaluate the impact of reducing the number of school occupants as a non-geometric change. The results showed that decreasing the number of occupants from 522 to 353 could lead to a reduction in total evacuation time by 128 s. Thus, this study identifies the large number of occupants as a significant factor contributing to extended evacuation times.
Our findings can inform the design and modification of school buildings to minimize evacuation times during emergencies, thereby reducing property damage and potential casualties. This study provides essential parameters for primary school stakeholders to consider when developing crisis management plans and revising national building regulations and design criteria for educational facilities to ensure the safe evacuation of students.
The results also indicated that the Required Safe Evacuation Time (RSET) significantly exceeded the Available Safe Egress Time (ASET) in all simulation modes.
Even in the last simulation, which involved reducing the number of students to 170 and resulted in a 128 s decrease in total evacuation time, the RSET (505 s) still surpassed the ASET (180 s). This disparity underscores the importance of implementing control measures to mitigate fire risks. Designing and installing fire alarm and extinguishing systems, along with conducting emergency evacuation exercises for students, can improve emergency evacuation conditions during a fire and minimize alarm and response times. Therefore, it is suggested that future studies investigate the effect of installing automatic fire alarms and extinguishing systems, as well as the impact of regular evacuation drills on reducing the RSET.
M.S., R.A. and V.Z. conceptualized the study and participated in the initial study design; M.S. and R.A. collected the data; M.S. simulated the emergency evacuation; M.S. and V.Z. obtained the research funding; V.Z. wrote the initial, revision and final manuscript; M.S. and M.A. revised the final manuscript. All authors have read and agreed to the published version of the manuscript.
This study was approved under the ethical approval code of IR.QUMS.REC.1401.196. Available online:
The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.
The authors declare no conflict of interest.
Footnotes
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Enlarge this image.Figure 9. Ambient temperature and smoke concentration in the corridor of the ground floor at 240 s.
Enlarge this image.Figure 10. Visibility and smoke concentration in the corridor of the ground floor at 180 s.
Enlarge this image.Figure 15. Schematic layout of the flow rate of occupants at different times (A–E).
Enlarge this image.Figure 16. Number of occupants remaining in school per unit of time; simulation based on all geometrical changes in the emergency evacuation process.
Enlarge this image.Figure 17. Change in the passenger flow rate over time; simulation based on all geometrical changes in the emergency evacuation process.
Enlarge this image.Figure 18. Number of occupants remaining in school per unit of time; the impact of the first change.
Enlarge this image.Figure 19. Number of occupants remaining in school per unit of time; the impact of the second change.
Enlarge this image.Figure 20. Number of occupants remaining in school per unit of time; the impact of the third change.
Enlarge this image.Figure 21. Number of occupants remaining in school per unit of time; the impact of the fourth change.
Enlarge this image.Figure 23. The number of people evacuated and the density of evacuation of floors 60.1 s from the start of emergency evacuation.
Enlarge this image.Figure 24. The number of people evacuated and the density of evacuation of floors 150.1 s from the start of emergency evacuation.
The area of the rooms in the school building and the number of people in them.
| Ground Floor | ||
|---|---|---|
| Room | Area of the rooms (m2) | Number of occupants |
| Management office 1 | 38.4 | 4 |
| Management office 2 | 62.88 | 4 |
| Health room | 12 | 1 |
| Pantry | 6.5 | 2 |
| Staff room | 30.72 | 3 |
| Education room | 19.44 | 1 |
| Class 1-1 | 33.6 | 31 |
| Class 1-2 | 33.6 | 30 |
| Class 1-3 | 33.6 | 31 |
| Class 1-4 | 33.6 | 32 |
| Class 1-5 | 33.6 | 28 |
| Class 2-2 | 33.6 | 31 |
| Class 2-3 | 33.6 | 31 |
| Class 3-5 | 33.6 | 33 |
| First Floor | ||
| Room | Area of the rooms (m2) | Number of occupants |
| Laboratory | 33.6 | 0 |
| Prayer room | 67.2 | 0 |
| Office room | 19.44 | 1 |
| Counseling room | 18.87 | 1 |
| Class 2-1 | 33.6 | 36 |
| Class 2-4 | 33.6 | 34 |
| Class 2-5 | 33.6 | 29 |
| Class 2-6 | 33.6 | 33 |
| Class 3-1 | 33.6 | 29 |
| Class 3-2 | 33.6 | 33 |
| Class 3-3 | 33.6 | 32 |
| Class 3-4 | 33.6 | 32 |
Characterization of occupants in the school building.
| Occupants | Total Number | Average Number per Class | Gender | Age (Year) | Height (cm) | Shoulder Width (cm) | Body Width (cm) | Health Status | Maneuver Experience |
|---|---|---|---|---|---|---|---|---|---|
| First Grade | 147 | 29.4 | Male | 7 | 118.93 | 29.66 | 31.00 | Health | Not |
| Second Grade | 188 | 31.33 | Male | 8 | 127.04 | 29.92 | 31.94 | Health | Not |
| Third Grade | 154 | 30.8 | Male | 9 | 132.95 | 30.52 | 33.25 | Health | Not |
| Staff | 27 | - | Female | 41 | 171.15 | 39.87 | 37.09 | Health | Not |
| Staff | 6 | - | Male | 39 | 181.19 | 42.12 | 39.18 | Health | Not |
Condition of evacuation scenario.
| Evacuation | Occupants | Environment Condition | Time Delay to Start an Evacuation | The Optimal Time Concerning the Daily Routines | A Commonly Used Free Travel |
|---|---|---|---|---|---|
| Fire started in the pantry on the ground floor | 262 | It is separated from other classes | For Schools = 240 s | all children are supposed to be in class with their teacher (522 occupants in total) | children (1–1.1 m/s) |
Comparison of the collected data with standard values.
| Parameter | The Measured Value of the Parameter/the Result of Parameter Evaluation (Qualitative) | Description of the Relevant Regulation About the | The Result of the Comparison | Standard Reference |
|---|---|---|---|---|
| Classroom area per pupil | Max = 1.2 m2/pers | The classroom area per pupil in urban primary schools is 1.75 m2 and the permitted capacity is 30 pupils. | Less than 1.75 m2 for all classes | The second chapter of the regulation of design criteria for educational buildings |
| Area of classes | 33.6 m2 | The area of classrooms in urban schools should be between 35 and 54 m2. | Less than 35 m2 for all classes | The second chapter of the regulation of design criteria for educational buildings |
| Opening direction of the doors of classrooms and staff rooms | indoor | Doors of all rooms should open outwards and in the direction of escape. | Inward/non-compliant with the standards | The fourth chapter of Iran’s national building regulations and the fourth chapter of regulation of design criteria for educational buildings |
Investigated geometrical change modes and their effects in the studied school.
| Name of the Floors | Number of Existing Stairs | Change in the Number of Existing Stairs in Simulation | Width of the Main Corridor (m2) | Change in the width of the Main Corridor in Simulation (m2) | Existing Area of the Classroom (m2) | Change in the Area of the Classroom in Simulation (m2) | Width of the Entrance/Exit Door of the Floor (m2) | Change in the Width of the | Opening | Opening |
|---|---|---|---|---|---|---|---|---|---|---|
| Ground floor | 1 | unchanged | 3.6 | 4.6 | 33.6 | 45 | 1.8 | 3.6 | Inward | Outward |
| First floor | 2 | unchanged | 3.6 | 4.6 | 33.6 | 45 | - | unchanged | Inward | outward |
The effect of school geometrical changes on reducing the duration of emergency evacuation.
| Import of All Changes in Simulation | Changing the Width of the Main Corridors in Simulation (m2) | Changing the | Changing the Width of the Main Entrance/Exit Door of the Ground Floor to 3.6 m2 | Changing the Area of the Classroom to 45 m2 | Changing the |
|---|---|---|---|---|---|
| 21.2 | Not noticeable | 3 | 4.2 | 17.5 | Reduced duration of emergency evacuation, seconds |
| 364.8 | 386 | 383 | 381.8 | 368.5 | Total time of evacuation, seconds (in this change) |
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; Amerzadeh, Mohammad 2 ; Zaroushani, Vida 3 1 Department of Occupational Health and Safety Engineering, Student Research Committee, School of Public Health, Qazvin University of Medical Sciences, Qazvin 34197-59811, Iran;
2 Social Determinants of Health Research Center, Research Institute for Prevention of Non-Communicable Disease, Qazvin University of Medical Sciences, Qazvin 34197-59811, Iran;
3 Social Determinants of Health Research Center, Research Institute for Prevention of Non-Communicable Disease, Qazvin University of Medical Sciences, Qazvin 34197-59811, Iran;