Egress Safety for STUDIO Residential Buildings

Abstract

In recent years, the number of studio residential buildings has increased significantly in Korea, as well as in many other countries, due to changes in living patterns. In Korea especially, there have been many fire accidents in studio residential buildings, which have caused a huge number of casualties and property damages, because the buildings were not adequately equipped for firefighting. In this study, the egress safety of a typical studio residential building in Korea is analyzed. Fire simulations were performed with variables of the fire location and the capacity of the smoke exhaust system to estimate the available safe egress time (ASET); egress simulations were also performed with the variable of egress delay time, and the required safe egress time (RSET) was determined. Then, the egress safety was evaluated, and the criteria for egress safety evaluation were proposed based on the simulation results. A studio residential building with a floor plan different from the prototype was used to validate the proposed egress safety criteria. Finally, a simple evaluation model is presented to estimate the required safe egress time (RSET) without simulation and to examine the impact of bottlenecks.

1. Introduction

As shown in

Table 1. Fire accidents in residential buildings.

Year	Fatalities (People)	Fire Occurrence (Cases)
2012	150	6663
2013	145	7163
2014	122	7559
2015	143	8170
2016	149	8179
2017	151	7995
2018	137	8037
2019	147	7539
2020	150	7531
2021	160	7636

, fire accidents in residential buildings continue to cause loss of life in Korea. In recent years, the number of one- and two-person households in Korea has increased significantly, and the number of small or studio residential buildings has grown accordingly. A studio residential building is a type of dwelling that contains a bedroom, living room, and kitchen in a single compartment. Because studio residential buildings can be advantageous for improving space efficiency in a small area by separating only the bathroom, their number has increased significantly in Korea since the mid-2000s, especially in cities with universities. Typically, in Korea, studio residential buildings are built in small sizes with fewer than five stories, and in such cases, the regulations against fire are very minimal. For this reason, studio residential buildings in Korea are not adequately equipped for fire and do not have sprinklers, smoke detectors, etc., which leads to a relatively huge number of casualties and property damages in the event of fire.

Several studies have been conducted on fire in residential buildings. Cvetković et al. [1] evaluated an occupant behavior model during a fire in a residential building in Serbia and reported that gender and age are the most important factors during fire egress. Yatim [2] investigated the factors affecting the design and specification of egress routes and egress time in high-rise residential buildings in Malaysia. Gautami et al. [3] presented the causes of fires and fire prevention measures in high-rise residential buildings through physical observations and questionnaire interviews. Kumar et al. [4] proposed a fire risk assessment index system for the elderly living in high-rise residential buildings in India. Akashah et al. [5] assessed the fire risk of high-rise residential buildings in Kuala Lumpur, Malaysia. Heo et al. [6] conducted an egress safety evaluation of a residential building based on the arrangement of the smoke exhaust system. While numerous studies [7,8,9,10,11,12,13] have aimed to assess the egress safety of diverse structures, including complex buildings, subways, nursing hospitals, and underground complexes, through fire and egress simulations, they primarily consist of case studies focusing on specific structures with predetermined sizes and floor plans, necessitating reruns of fire and egress simulations after any alterations.

As previously mentioned, small studio residential buildings in Korea are not required to have adequate equipment against fire, and in addition, there is no requirement to evaluate the egress safety of residential buildings. On the other hand, the cost of conducting fire and egress simulations is relatively high. Therefore, this study aims to perform an egress safety evaluation on small studio residential buildings and to provide criteria for evaluating the egress safety of small studio residential buildings without conducting fire and egress simulations.

Figure 1 shows a flowchart that illustrates all the procedures for the derivation of the egress safety criteria in this study. The first step was fire simulation. Fire scenarios were set up at two fire locations and seven smoke exhaust system capacity levels were used as variables, and the available safe egress time (ASET) was calculated for each case. The second step was egress simulation. Egress scenarios were set up for nine egress delay time cases, and the required safe egress time (RSET) was calculated for each case. In the third step, the egress safety was evaluated for each case by comparing the ASET and the RSET. In the last step, the egress safety criteria were presented, based on the simulation results. In addition, the proposed criteria were validated by applying them to a small studio building with a floor plan that was different to that of the prototype building and by comparing the simulation results.

2. Fire Dynamic Simulation Model and Results

The Fire Dynamics Simulator (FDS) [14] has been widely used in fire simulations and has been rigorously validated through a wide range of studies [15,16,17,18]. Accordingly, in this study, FDS was selected to model fire scenarios in studio residential buildings. Figure 2 shows the floor plans of typical studio residential buildings. The floor plans can be classified into four types: one-sided corridor type, mid-corridor type, central hallway type, and mid-hallway type. The egress characteristics in case of fire are different depending on the floor plan. In this study, as shown in Figure 3, the mid-corridor type studio building was set as the prototype building because it is the most common type in Korea. The mid-corridor type studio building has a single exit in the center of the building, and the building was assumed to have a floor height of 2.75 m and a floor area of 29.8 m × 14.0 m. The fire location was set to be directly over the corridor, i.e., Location ①, and in the room on the southeast side, i.e., Location ②, and the burning area was planned to be 1 m². All smoke exhaust systems were assumed to be installed in the corridor. In Korea, the capacity of the smoke exhaust system is determined according to the standards presented by the Korean Fire Protection Association [19]. The capacity of the smoke exhaust system of the prototype building presented by KFPA is 12.5 m³/s, and in this study, a total of seven capacity levels of smoke exhaust systems (0%, 25%, 50%, 75%, 100%, 125%, and 150%) were examined, as shown in

Table 2. Analysis cases according to capacity levels of smoke exhaust system.

Name of Analysis Cases	Levels of Smoke Exhaust System (%)	Capacity of Smoke Exhaust System (m3/s)	Velocity of Exhaust System (m/s)
S-0	0	0	0
S-25	25	3.125	0.059
S-50	50	6.25	0.118
S-75	75	9.375	0.177
S-100	100	12.5	0.236
S-125	125	15.625	0.294
S-150	150	18.75	0.353

, considering 12.5 m³/s (100%) as the reference capacity of the smoke exhaust system. To simulate a worst-case scenario, the FDS analysis assumed conditions where openings such as doors were open.

As shown in

Table 3. Fire loads of combustibles.

Furniture	Heat Release Rate, HRR (kW)	Main Material (CO Yield (g/g), Soot Yield (g/g))	Total HRR (kW)	Fire Growth Coefficient, α	Ramp-Up Time, t2 (s)
Desk	422.5	Polyurethane Foam (0.042, 0.198)	6598.52	0.01172	750.34
Chair	84	Polyurethane Foam (0.042, 0.198)
TV	274	Plastic (0.028, -)
Refrigerator	1148	Plastic (0.028, -)
Bed	193.22	Polyester (0.015, -)
Sofa (small)	1538	Polyether Foam (0.029, 0.008)
Closet	2938.8	Wood (0.004, 0.015)

, the combustibles in a room of the studio building were assumed to be typical furniture such as desk, chair, television, refrigerator, bed, sofa, and closet. The heat release rate (HRR) of each combustible was obtained from the National Center for Forensic Science (NCFS) database [20], and the fire load was calculated by summing the HRR of all combustibles as 6598 kW (1,648,125 kJ/m²). The fire growth rate was calculated using the t-squared fire growth model [21], as shown in Figure 4. The fire growth type was determined as medium according to the usage of the building, and the fire growth coefficient of 0.0117 was applied accordingly. As shown in Figure 5, the fire simulation modeling was performed by referring to the “Fire Dynamic Simulator User’s Guide” [14], and with reference to this, the size of the mesh was calculated as:

$$D^{*}={\left({\displaystyle \frac{\stackrel{•}{Q}}{{\rho }_{\infty }{c}_p{T}_{\infty }\sqrt{g}}}\right)}^{2/5}$$

(1)

$$4\le D^{*}/dx\le 16$$

(2)

where $\dot{Q}$ is heat release rate (kW), ${\rho }_{\mathrm{\infty }}$ is the density of the ambient air (1.204 kg/m³), $c_p$ is the specific heat of the ambient air (1.005 kJ/kg-K), $T_{\mathrm{\infty }}$ is the temperature of the ambient air (293 K), $g$ is the gravitational acceleration (9.81 m/s²), $D^{\mathrm{*}}$ is characteristic fire diameter (m), and $dx$ is the size of the mesh (m). According to Equation (1), the mesh size was calculated as 0.2 m × 0.2 m × 0.19 m, and the moderate mesh value with a $D^{\mathrm{*}}/dx$ value of approximately 10.8 was selected considering the constraints shown in Equation (2). The height of the detector device was 1.8 m, and temperature, carbon monoxide, carbon dioxide, and oxygen and visibility sensors were installed. The primary purpose of this study is to provide criteria for evaluating egress safety, and the results should be relatively conservative. As shown in Table 3, for conservative evaluation, polyurethane foam was used as the most dangerous material among the main materials of the furniture arranged in the studio building. The CO yield and soot yield were assumed to be 0.042 and 0.198, respectively [22].

Figure 6 shows the smoke behavior according to the capacity levels of the smoke exhaust system. Figure 6a–c are the results at 200, 400, and 800 s after the fire in the absence of the smoke exhaust system (Case S-0). At 400 s after the fire broke out, smoke had spread to all units in the studio building. Figure 6d–f show Case S-25, where the capacity of the smoke exhaust system is 25% of the reference capacity, and it is observed that the smoke was relatively well controlled compared to Case S-0. Comparing Case S-100 (Figure 6g–i) and Case S-150 (Figure 6j–l), it is also shown that the greater the smoke exhaust capacity, the better the smoke control.

Figure 7 shows the results of visibility, carbon monoxide (CO), temperature, oxygen (O₂), and carbon dioxide (CO₂) on the right front of Exit A in Case S-0. In the figure, the red dotted lines represent the tenability criteria provided by [23], as shown in

Table 4. Tenability criteria by NFPA [23].

Design Criteria	Tenability Limit
Temperature	<60 °C
Visibility	>5 m
Carbon monoxide (CO)	<1400 ppm
Carbon dioxide (CO2)	<5%
Oxygen (O2)	>15%

.

The time for each datapoint to reach the red dotted line is determined as the ASET by each factor, and the lowest value of the ASET by the five factors is determined as the ASET of the studio building. As shown in Figure 7, all five factors resulted in lower ASETs in the case of fire Location ① compared to those in the case of fire Location ②. The lowest value of the ASET under the fire Locations ① and ② can be determined as the ASET of the studio building at 100 s and 243 s, respectively. This implies that a fire closer to the exit provides less margin of safety for egress in cases of studio buildings where the combustibles in all rooms are similar. These results do not change even when the smoke exhaust system is installed. Therefore, the ASET for the prototype studio building was determined from the ASET results for the case of fire Location ①. In addition, visibility has the lowest ASET of the five factors, even when the capacity of the smoke exhaust system increases. In other words, the ASET was determined by visibility.

Table 5. Available safe egress times according to capacity of smoke exhaust system.

Case	S-0	S-25	S-50	S-75	S-100	S-125	S-150
Capacity of smoke exhaust system	0 (m3/s)	3.125 (m3/s)	6.25 (m3/s)	9.375 (m3/s)	12.5 (m3/s)	15.625 (m3/s)	18.75 (m3/s)
ASET (s)	100	174	226	252	276	287	310

shows the results of the visibility according to the capacity of the smoke exhaust system. As the capacity of the smoke exhaust system increases, the ASET also increases. In particular, when the capacity of the smoke exhaust system was installed according to the standards specified by the Korean Fire Protection Association (i.e., Case S-100) [19], the ASET increased by 176% compared to the case without the smoke exhaust system (Case S-0). In this study, the burner was modelled at 1 m². This may from modelling the actual size of the furniture. Also, the location of the exhaust can affect the simulation results. In Appendix A, the simulation results were compared according to the burner size and the smoke exhaust system location. These two variables had no significant effect on the simulation results.

3. Egress Simulation Model and Results

In this study, simulations were conducted to evaluate the egress performance of the studio building by Pathfinder [24]. Pathfinder provides an easy way to estimate the egress time for all occupants. Figure 8 shows the Pathfinder model of the studio building. The building was assumed to have five floors without an elevator. Note that buildings less than or equal to five stories are not required to have elevators in Korea. Egress simulations require assumptions about the number, speed, and width of occupants in the building. The number of occupants was determined by the minimum area for one person suggested by the Ministry of Land, Transport and Maritime Affairs [25], that is, 14 m², based on which, in this study, 22 people are assumed to live on each floor of the studio building. It was also assumed that 50% of the occupants were male and 50% were female, and the widths and speeds of the occupants were adopted from the study by Bohannon and Andrews [26]. The egress speeds ranged from 1.192 to 1.502 m/s for males and from 1.110 to 1.431 m/s for females [26]. The widths of the male and female were also assumed as 40 cm, and 35.8 cm, respectively [26].

When a fire occurs in a building, there exists a period of time between the onset of the fire and the initiation of egress. This interval encompasses various stages, including fire detection, the activation of alarm systems, and occupants’ awareness and response to the alarm. Termed as the egress delay time, this duration plays a crucial role in evacuation planning and safety measures. The Ministry of Public Safety and Security of Korea [27] provides recommendations regarding egress delay times, taking into account factors such as building usage, alarm systems, and CCTV surveillance, among others. In this study, the egress delay time is considered as a variable in the egress simulation. While egress delay times are conventionally measured in minutes, this study employs 30 s intervals to facilitate a more granular analysis. The egress delay time considered in this study ranges from 0 to 210 s. In the simulation, occupants in the area directly affected by the fire are assumed to initiate egress immediately upon detection. Conversely, occupants in other areas are presumed to commence egress after the lapse of the designated egress delay time.

Figure 8 illustrates the required safe egress time (RSET), representing the duration necessary for all occupants to complete egress safely. When the egress delay time is set to 0, indicating immediate egress initiation upon the onset of the fire, the results indicate that all occupants successfully complete egress within 107 s. As the egress delay time increases, the RSET also increases accordingly. For instance, with an egress delay time of 210 s, the RSET extends to 317 s. This indicates that the longer the delay in initiating egress after the fire occurrence, the more time it takes for all occupants to egress the building safely. Such insights are crucial for emergency planning and optimizing egress procedures to ensure the safety of building occupants.

4. Evaluation of Egress Safety Criteria

4.1. Evaluation of Egress Safety

Comparing the available safe egress time (ASET) with the required safe egress time (RSET) allows for the evaluation of egress safety. When the ASET exceeds the RSET, all occupants can successfully evacuate, and the difference between the ASET and the RSET represents the safety margin. Conversely, if the ASET is less than the RSET, some occupants may fail to egress. Table 5 presents the number of individuals who failed to egress in each scenario, based on the number of occupants on the 5th floor, which is deemed most vulnerable during egress. The number of failed evacuees was counted as the number of people in the building at the time the ASET was completed. As observed, the number of individuals failing to egress increased with the elongation of the egress delay time and the reduction in the capacity of the smoke exhaust system. In the absence of a smoke exhaust system (Case S-0), even with immediate egress initiation (i.e., egress delay time of 0), five individuals failed to egress. Notably, installing a smoke exhaust system operating at 25% of the reference capacity (Case S-25) provided a 60 s egress delay. Moreover, with the smoke exhaust system functioning at 100% of the reference capacity (Case S-100), successful egress was achieved even when egress commenced 150 s after the fire broke out. This highlights the critical role of the smoke exhaust system in facilitating timely and safe evacuation. Furthermore, it underscores the importance of considering egress delay time and smoke exhaust system capacity in enhancing building safety measures and ensuring effective emergency response protocols.

The Korean Fire Protection Association [19] mandates that the capacity of the smoke exhaust system be determined based on the floor area of the building. Similarly, the Ministry of Public Safety and Security of Korea [27] provides deterministic egress delay times based on the building’s usage and alarm systems. However, as indicated in

Table 6. Egress simulation results (number of failed evacuees).

	Egress Delay Time (s)	0	30	60	90	120	150	180	210	240
Capacity of Exhaust System (%)
0		5	16	22	22	22	22	22	22	22
25		0	0	0	13	22	22	22	22	22
50		0	0	0	0	1	17	22	22	22
75		0	0	0	0	0	3	19	22	22
100		0	0	0	0	0	0	7	21	22
125		0	0	0	0	0	0	1	16	22
150		0	0	0	0	0	0	0	5	20

, egress safety exhibits significant variability depending on both the capacity of the smoke exhaust system and the egress delay time. Therefore, it is deemed more reasonable to propose that the determination of the smoke exhaust system’s capacity should be informed by the results of egress safety evaluations. This approach would involve considering both the capacity of the smoke exhaust system and the egress delay time. By assessing the effectiveness of various combinations of smoke exhaust system capacities and egress delay times in ensuring egress safety, building designers and safety officials can tailor smoke exhaust system capacities more precisely to the specific requirements of each building. This adaptive approach acknowledges the dynamic and multifaceted nature of building safety and emergency response, thereby enhancing overall safety measures.

4.2. Egress Safety Criteria

Given the absence of mandatory egress safety evaluations for studio buildings in Korea and the significant time and cost associated with fire and egress simulations, it is understandable that egress safety assessments are often overlooked in this context. Additionally, building managers may lack specialized knowledge of fire and egress dynamics, further complicating safety evaluations. In response to these challenges, there is a clear need for the development of simplified criteria that non-experts can use to assess the safety of studio buildings. Such criteria should be easy to understand and apply, enabling building managers and stakeholders to identify potential safety concerns and implement necessary measures to mitigate risks.

The egress safety criteria presented in Figure 9 were derived from the findings of the egress safety evaluation outlined in Table 5. The x-axis of the figure represents the egress delay time, while the y-axis denotes the capacity of the smoke exhaust system divided by the building’s floor area. The line on the graph serves as a standard for distinguishing between safe and unsafe scenarios. Cases falling above the line were deemed safe in the egress safety evaluation, whereas cases below the line were considered unsafe. These criteria have been proposed to provide a concise means of assessing the egress safety of mid-corridor type studio buildings, utilizing parameters such as the capacity of the smoke exhaust system, building area, and egress delay time. They offer a practical tool for evaluating the egress safety of studio buildings currently in use or under design, and for establishing additional safety measures as needed. In cases where the egress safety evaluation indicates an unsafe scenario, these criteria can help determine the necessary adjustments to ensure safety. This might involve reducing the egress delay time or increasing the capacity of the smoke exhaust system to meet egress safety standards.

It is important to note that the egress safety criteria presented in this study are specifically tailored for mid-corridor type studio buildings. They may not be directly applicable to other types of studio buildings, such as one-sided corridor type, central hallway type, or mid-hallway type studio buildings. Also, further validation is needed to ascertain whether these criteria can be effectively applied to mid-corridor type studio buildings of varying sizes. Such validation could help refine and adapt the criteria to suit different building configurations and dimensions, ensuring their broader applicability and effectiveness in enhancing egress safety.

5. Validation

Figure 10 shows a new studio building for validation of the egress safety criteria proposed in this study. It is a mid-corridor studio building that has the same floor type as the prototype building, but its size and floor plan are somewhat different from the prototype. The ASET and the RSET were determined by performing fire and egress simulations on a five-stories studio building measuring 24.8 m × 11.3 m, and the evaluation results were compared and analyzed with the results of the proposed egress safety criteria.

Figure 11a illustrates a fire simulation model of a studio building used for validation purposes. In this model, the capacity of the smoke exhaust system was assumed to be 3.125 m²/s, which corresponds to 25% of the reference capacity. The smoke exhaust system was installed in the corridor. The fire location was selected as a room adjacent to the exit, representing a worst-case scenario. The assumptions for the fire simulation align with those presented in Section 2 (Fire Dynamic Simulation Model and Results). The ASET was determined to be 190 s based on visibility considerations, as shown in Figure 11b.

Figure 12 presents an egress simulation model of a residential building for validation purposes. Considering the floor area of the building, it was assumed that 15 people resided on one floor. The egress delay time was evaluated at 30 s intervals. The width and speed of the occupants were consistent with those outlined in Section 3 (Egress Simulation Model and Results). It appears that in scenarios where the smoke exhaust system capacity was set at 25% and the egress delay time was 0 s, all occupants successfully completed egress within 85 s. As the egress delay time increased, the success of evacuation became compromised. While all occupants were able to egress successfully when the egress delay time was 60 s, none of the occupants on the 5th floor managed to complete egress when the egress delay time exceeded 120 s.

Figure 13 shows the results of evaluating the egress safety of the studio building presented in Figure 10 using the proposed egress safety criteria. The floor area of the studio building divided by the capacity of the smoke exhaust system was 52.6 m per hour. The maximum egress delay time to ensure egress safety was approximately 82 s. Upon considering the egress delay time at 30 s intervals, the evaluation indicates that egress safety is achieved when the egress delay time ranges from 0 to 60 s. However, beyond this threshold, from 60 to 240 s, the scenario is deemed unsafe in terms of egress safety. Remarkably, these observations closely mirror the results obtained from the egress safety evaluation conducted using fire and egress simulations, as depicted in Figure 12. This consistency reaffirms the reliability and validity of the proposed egress safety criteria in assessing the safety of studio buildings during emergency evacuation scenarios.

In this study, a simple evaluation was proposed to derive the RSET for evacuation safety evaluation without performing complex egress simulation. A timeline of the determinants of the RSET is shown in Figure 14. The factors that affect the RSET can be broadly categorized as the delay time (T_d) before evacuation begins and the evacuation time (T_e) after evacuation begins. Here, the delay time includes the detection time (T_de) to detect the fire, the alarm time (T_a) to disseminate the fire situation through the alarm, and the occupant’s recognition time and response time (T_r+r) to the fire situation, which are determined by the building’s use, alarm system, CCTV, etc. In this study, the evacuation time was categorized into three types of times. The first is the movement time (T_m) from the occupant’s current location to the doorway, which is calculated by dividing the total distance traveled by the occupant by the occupant’s egress speed. The second is the stair travel time (T_s) for occupants to travel down the stairs, which, like T_m, is calculated by dividing the distance traveled down the stairs by the occupants’ stair travel speed. The third is the bottleneck time (T_b) that occurs during occupant evacuation. It is difficult to estimate the exact value of T_b because it is affected by many factors, such as the width of the hallway, the width of the stairs, the width of the door, and the total number of occupants. Therefore, in this study, T_b was estimated by comparing simulation results with a simple evaluation.

Generally, the RSET is determined by the person with the greatest distance from the occupant’s current location to the exit. The occupant at that location may be determined based on the slowest moving occupant in the building by age and gender. As shown in Figure 15, a simple evaluation model for the RSET of a mid-corridor type residential building was presented in this study. The proposed model is determined by building y-axis length, building x-axis length, outermost room length, outermost room width, stair stringer length, landing length, minimum walking speed, and number of floors. The movement length of a mid-corridor residential building was the distance from the exit to the exit from the position farthest from the exit in the floor plan (the center of the room). The stair length was calculated by considering the distance traveled to go down the stairs to the first floor.

Figure 16 shows the results of deriving the RSET of the prototype residential building and the validation case residential building by the proposed evaluation model and comparing them with the egress simulation results. The RSETs of the prototype residential building and the validation case residential building were calculated to be 84.4 s and 68.1 s, respectively, assuming that the egress delay time and the bottleneck time are 0 s. According to the previous egress simulation results, the RSETs of the prototype residential building and the validation case residential building were 107 s and 85 s, respectively, when the egress delay time was 0 s. The difference between the proposed simple evaluation model and the egress simulation showed 19.8% and 21.1% in the two cases, respectively, which is judged to be affected by the bottleneck at the exit as shown in Figure 17. In other words, T_b can be calculated to be 22.6 and 16.9 s in the two cases, respectively. Even for a residential building with a relatively small number of occupants, it is estimated that bottlenecks can cause evacuation delays (T_b) of 20% of the RSET. This will increase as the number of occupants increases and the width of the exit becomes narrower. Using the proposed simple evaluation model, it is possible to quantitatively evaluate the time caused by bottlenecks.

6. Discussion

The utilization of the proposed criteria shown in Figure 13 offers a streamlined approach to evaluating egress safety for studio buildings without the need for extensive fire and egress simulations. By leveraging information on the building’s floor area, capacity of the smoke exhaust system, and egress delay time, building managers, safety officials, and designers can assess egress safety efficiently and effectively. One of the key advantages of these criteria is their versatility in accommodating changes to the building’s floor plan or layout. Unlike traditional fire and egress simulations, which require significant time and resources and must be repeated for each variation in the floor plan, the proposed criteria allow for quick and straightforward evaluations based on readily available information. Moreover, the flexibility of the proposed criteria enables adjustments to be made to the capacity of the smoke exhaust system and the egress delay time to ensure egress safety in a given studio building. This adaptability allows for tailored solutions that address specific safety concerns and optimize egress procedures.

While the proposed criteria have proven useful for evaluating the egress safety of mid-corridor type studio buildings, it is acknowledged that different criteria may be necessary for other types of studio buildings, such as one-sided corridor types, central hallway types, and mid-hallway types. Therefore, further research and development may be required to establish criteria tailored to these specific building configurations.

Overall, the proposed criteria represent a valuable tool for enhancing egress safety in studio buildings and contribute to the development of efficient and cost-effective safety assessment methodologies.

7. Conclusions

The study conducted fire simulations with varying fire locations and smoke exhaust system capacities to determine available safe egress times (ASETs), and egress simulations with different egress delay times to establish the required safe egress times (RSETs). Egress safety was then evaluated by comparing the ASETs and the RSETs, leading to the proposal of criteria for determining egress safety without the need for simulation every time. Furthermore, these criteria were validated using a studio building with a floor plan different from that of the prototype. The study yielded the following conclusions.

• Fire Simulation Findings: Fire simulations identified fire locations near exits as the worst-case scenario. The ASET was determined to be primarily influenced by visibility rather than the smoke exhaust system’s capacity.
• Effect of Smoke Exhaust System Capacity and Egress Delay Time: Increasing the capacity of the smoke exhaust system correlated with higher ASET values, while longer egress delay times resulted in higher RSET values.
• Determining Smoke Exhaust System Capacity: The study proposed that the capacity of the smoke exhaust system can be reasonably determined based on the results of egress safety evaluations, considering both the system’s capacity and the egress delay time.
• Proposed Criteria for Egress Safety Evaluation: Criteria for evaluating egress safety in mid-corridor type studio buildings were presented. These criteria were found to effectively assess egress safety across various studio building sizes and could aid in establishing supplementary safety measures. However, it was noted that separate criteria may be necessary for different types of studio buildings, such as one-sided corridor type, central hallway type, and mid-hallway type studio buildings.
• Bottleneck delay: A simple evaluation model was presented to estimate the RSET without egress simulation. By comparing the results from the simple evaluation model and the egress simulation, the delay caused by bottlenecks was quantitatively evaluated.