⚡ electrical engineering

Fire Evacuation Strategies for Hospital Inpatient Wards under Different Fire Source Locations

This study utilizes PyroSim and Pathfinder simulations to analyze fire scenarios and evaluate evacuation strategies for a high-rise hospital ward in China, demonstrating that optimizing exit selection, occupant priority, and refuge areas based on fire source location significantly improves evacuation efficiency and safety.

Original authors: Peixu Zhang, Siqi Liu, Xiaolu Wang, Yanru Bao, Yunling Gao, Yanan Chen, Jiquan Zhang

Published 2026-06-29

📖 4 min read☕ Coffee break read

CC BY 4.0

Original authors: Peixu Zhang, Siqi Liu, Xiaolu Wang, Yanru Bao, Yunling Gao, Yanan Chen, Jiquan Zhang

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

Imagine a hospital ward as a busy, multi-story apartment building where the "residents" are patients. Some residents are energetic and can walk on their own, some need a wheelchair, and others are bedridden and need to be carried. Now, imagine a fire breaks out. The goal of this study is to figure out the fastest, safest way to get everyone out before the smoke and heat become deadly.

The researchers treated this like a video game simulation. They built a digital twin of a real hospital in China and ran two types of simulations: one to see how the fire and smoke behave, and another to see how people move.

Here is the breakdown of their findings in simple terms:

1. The "Smoke Monster" and the Clock

First, they had to figure out how much time people actually had before the building became too dangerous to be in. They looked at three things:

Heat: If the air gets too hot (like a sauna that's too hot to stand in), it burns you.
Toxic Gas: Carbon monoxide is like an invisible thief that steals your ability to breathe.
Visibility: This was the biggest problem. Smoke is like thick fog. If you can't see your hand in front of your face, you can't find the exit.

They found that visibility was the most critical factor. In some scenarios, the smoke filled the hallways so fast that people had less than two minutes to get to a safe stairwell.

2. The "Traffic Jam" Problem

The researchers tested five different ways to evacuate the building, like testing different traffic rules on a highway.

Scenario 1 (Chaos): Everyone runs for the nearest door.
- Result: Disaster. Everyone crowded into one exit (Exit 02), creating a massive traffic jam. The other exits were almost empty. It took nearly 17 minutes to get everyone out.
Scenario 2 (The Traffic Cop): A "traffic cop" directs specific groups to specific doors. Bedridden patients go to one door, wheelchair users to another, and walking patients to the rest.
- Result: Much better. By spreading the crowd out, the "traffic jam" was broken. The evacuation time dropped by about 25%.
Scenario 3 & 4 (The Priority Pass): They added a rule where the most vulnerable people (bedridden and wheelchair users) get "priority passes" to move first.
- Result: This helped a little, but not as much as simply directing people to different doors. In fact, if you only give priority but don't fix the traffic flow, people still get stuck.
Scenario 5 (The Safe Room): They added a "Safe Room" (a refuge area) on the floors. Bedridden patients don't go down the stairs immediately; they wait in this safe room until the fire is under control or help arrives.
- Result: This was the winner. By keeping the slowest-moving people out of the stairwells, the "highway" cleared up for everyone else. The total evacuation time was cut in half compared to the chaotic scenario.

3. The Fire Location Matters

The researchers also found that the location of the fire changes the rules of the game:

Fire in the Middle: If the fire is in the middle of the hallway, the "Safe Room" strategy (Scenario 5) is best because it keeps bedridden patients safe while others run.
Fire at the Door: If the fire starts right next to a stairwell door, that door becomes a trap. No matter how good your plan is, if the exit is on fire, you can't use it. In these cases, the plan must change instantly to use a different door, and everyone needs to react faster.

The Big Takeaway

The study concludes that you can't just tell everyone to "run for the exit." In a hospital, you have to be a smart traffic manager.

Don't let everyone crowd one door. Assign different groups to different exits.
Don't make the slowest people run down the stairs if you have a safe room to wait in. This prevents them from blocking the faster people.
Watch the smoke. If the smoke is thick, you have very little time, so your plan needs to be perfect from the very first second.

By using these smart strategies, hospitals can save lives and get people out much faster than if they just let everyone panic and run.

Technical Summary: Fire Evacuation Strategies for Hospital Inpatient Wards under Different Fire Source Locations

Problem Statement
Hospital inpatient wards present unique challenges for fire evacuation due to the high density of occupants, the vulnerability of patients (including immobile and bedridden individuals), and the complex building layouts typical of high-rise medical facilities. Existing research often focuses on general evacuation dynamics or fire spread in isolation, frequently neglecting the critical interaction between specific fire source locations and the resulting evacuation constraints. In high-density public spaces, the combination of patient immobility and smoke hazards can lead to severe congestion, stagnation, and increased casualty risks. This study addresses the gap in developing tailored evacuation strategies that account for both the dynamic spread of fire hazards and the specific mobility limitations of hospital occupants.

Methodology
The study employs a two-stage simulation framework using a case study of a 12-story secondary hospital inpatient department in China.

Fire Dynamics Simulation (PyroSim):
- Scenario Design: Three distinct fire scenarios were modeled on the sixth floor (a heavily populated inpatient level) to test the impact of fire source location:
  - Scenario A: Fire located between the two stairwells.
  - Scenario B: Fire near the entrance of Stairwell 1.
  - Scenario C: Fire near the entrance of Stairwell 2.
- Parameters: The fire was modeled as a "fast" growth fire ( $\alpha = 0.04689 \, kW/s^2$ ) with a maximum heat release rate of 2.5 MW.
- Hazard Analysis: The simulation tracked smoke layer height, temperature, CO concentration, and visibility. Critical thresholds were established based on human tolerance limits (e.g., visibility < 5 m, temperature > 60°C, CO > 500 ppm) to determine the Available Safe Egress Time (ASET).
Evacuation Simulation (Pathfinder):
- Occupant Modeling: The model included 787 occupants (300 patients, 300 caregivers, 187 medical staff). Patients were categorized by mobility: 13% bedridden, 17% wheelchair-bound, and 30% immobile. Evacuation speeds were assigned based on gender, age, and mobility status.
- Behavioral Settings: The "Steering" mode was used to simulate dynamic path planning and collision avoidance. A 60-second pre-evacuation response time was assumed.
- Strategy Testing: Five evacuation strategies were simulated and compared against the ASET:
  - S1: Unorganized evacuation (Control group).
  - S2: Differentiated exit assignment (e.g., bedridden patients directed to specific exits).
  - S3: S1 with occupant priority settings (prioritizing vulnerable groups).
  - S4: S2 with occupant priority settings.
  - S5: S4 with the addition of designated refuge areas on floors above the third level.

Key Results

ASET Determination: Visibility was identified as the most critical limiting factor across all scenarios. In Scenario A, the sixth-floor corridor became unsafe within 100–250 seconds depending on the exit. In Scenario B, the time window was significantly shorter (61–166 seconds). In Scenario C, the fire location blocked Stairwell 2, rendering it unsafe for evacuation.
Evacuation Efficiency (ASET vs. RSET):
- Unorganized Evacuation (S1): Resulted in the longest evacuation time (986.9 s) and severe congestion at Exit 02/Stairwell 2, failing to evacuate sixth-floor patients safely in Scenarios A and B.
- Differentiated Exits (S2): Reduced total evacuation time to 727.9 s by balancing exit usage. However, congestion persisted due to the slow movement of bedridden patients.
- Priority Settings (S3 & S4): Implementing priority alone (S3) reduced time by 9% compared to S1 but was less effective than exit differentiation. Combining priority with exit differentiation (S4) yielded the best result among non-refuge strategies (667.5 s).
- Refuge Areas (S5): The inclusion of refuge areas for bedridden patients resulted in the most efficient evacuation (427 s). By preventing bedridden patients from entering the stairwells immediately, congestion was significantly reduced, and the overall evacuation curve became smoother.
Scenario-Specific Outcomes:
- In Scenario A, S5 was the only strategy ensuring safe evacuation for all occupants within the ASET.
- In Scenario B, even the optimized strategies (S4 and S5) could not evacuate occupants within the ASET (61 s) given the standard 60 s response time. Safe evacuation was only possible if the response time was reduced to 23 s (S5) or 18 s (S4).
- In Scenario C, closing Stairwell 2 and rerouting evacuees to Stairwell 1 allowed for safe evacuation under S4 and S5 strategies.

Key Contributions

Integrated Simulation Approach: The study successfully integrates fire dynamics (PyroSim) and pedestrian evacuation (Pathfinder) to evaluate evacuation strategies under specific fire source constraints, rather than treating them as independent variables.
Strategy Optimization: The research demonstrates that while priority settings help, the physical allocation of exits and the use of refuge areas are far more impactful in reducing evacuation times for hospital wards.
Refuge Area Efficacy: The study provides quantitative evidence that refuge areas significantly reduce total evacuation time by decoupling the movement of immobile patients from the main evacuation flow in stairwells.
Location-Dependent Strategies: The findings highlight that a single evacuation plan is insufficient; strategies must be adapted based on the fire's proximity to stairwells and exits.

Significance and Claims
The paper claims that its findings provide practical, actionable strategies for fire safety management in high-rise hospital wards. By identifying that visibility is the primary hazard and that exit allocation combined with refuge areas offers the most robust solution, the study offers a pathway to effectively reduce casualties. The authors emphasize that evacuation plans must be dynamic, adjusting exit routes and response protocols based on the specific location of a fire source to ensure occupants can evacuate within the Available Safe Egress Time. The study concludes that optimizing exit selection, setting occupant priorities, and implementing refuge areas are essential components for enhancing safety in complex medical evacuation scenarios.

1. The "Smoke Monster" and the Clock

2. The "Traffic Jam" Problem

3. The Fire Location Matters

The Big Takeaway

Technical Summary: Fire Evacuation Strategies for Hospital Inpatient Wards under Different Fire Source Locations

More like this