Evacuation strategies, 'Stay Put' vs 'Simultaneous Evacuation'

Q(Eam Taekyoung) : Evacuation strategies in the event of fire may change as the situation changes. However, basically, it seems necessary to understand that the Stay put strategy is an appropriate strategy to use when all three conditions below are met.

1. The building is designed to be fire-resistant, so each floor or apartment can be isolated from fire for a certain period of time.

2. Supply pressure smoke suppression equipment that protects the evacuation route from smoke infiltration is not installed.

3. Fire brigade can arrive quickly.

A(ChatGPT 4) : In the context of fire safety and evacuation strategies, the "Stay Put" policy is indeed a strategy that is employed under specific conditions, primarily in certain high-rise buildings. This approach is based on several key factors:

1. Fire-Resistant Design: Buildings that are suitable for a "Stay Put" strategy are typically designed with fire-resistant materials and structures. Each floor or apartment is constructed to be isolated from fire for a significant period. This containment design aims to prevent the rapid spread of fire and smoke, allowing occupants to remain safely in their apartments or designated areas for a considerable duration.

2. Absence of Comprehensive Smoke Suppression Systems: In situations where there are no advanced smoke suppression systems (like pressurized stairwells or hallways) to protect evacuation routes, the "Stay Put" policy might be more suitable. In many buildings, especially older ones, these systems might not be in place, making traditional evacuation more hazardous due to the risk of smoke inhalation in escape routes.

3. Rapid Response from Fire Services: The effectiveness of a "Stay Put" strategy is also contingent on the prompt response of the fire brigade. Quick arrival and action by firefighters can significantly mitigate the risk to occupants, as they can start battling the fire and rescuing individuals if necessary, before the situation escalates.

It's important to note that the "Stay Put" policy is not universally applicable. It is generally used in specific building types where evacuation is not immediately necessary or could even be more dangerous due to the building's layout, the potential for causing panic, or the risk of encountering smoke-filled escape routes. Residents of such buildings are often advised to stay in their apartments unless the fire is in their unit or they are otherwise in immediate danger.

The decision to implement a "Stay Put" policy should be based on a thorough risk assessment and in consultation with fire safety experts and local fire services. Regular fire drills and safety education for the occupants are also crucial for the success of such a strategy. Additionally, it's important for residents to be aware of the fire safety plan for their building and to follow the instructions of building management and fire services during an emergency.

Q(Eam Taekyoung) : Unlike the Stay put strategy above, the Simultaneous evacuation strategy appears to be an evacuation strategy that can be applied in principle to any specific building that has a supply pressurized smoke control system installed and a smokeproof enclosure applied.

A(ChatGPT 4) : The "Simultaneous Evacuation" strategy, as you've described, is indeed another approach to fire safety, contrasting with the "Stay Put" strategy. This method is particularly relevant in buildings equipped with certain fire safety features like pressurized smoke control systems and smokeproof enclosures. Here's how it works and why it's effective in certain situations:

1. Pressurized Smoke Control Systems: These systems are designed to prevent smoke from infiltrating evacuation routes, such as stairwells and hallways. By maintaining a higher air pressure in these areas compared to the areas where the fire is present, smoke is prevented from entering and obstructing these critical escape paths. This ensures that the routes remain clear and safe for evacuation.

2. Smokeproof Enclosures: These are specially designed areas or components in a building that resist the penetration of smoke. They are often used in conjunction with pressurized smoke control systems to further enhance the safety of evacuation routes. Smokeproof enclosures provide a safe haven and a clear path for occupants fleeing from a fire.

3. Applicability to Various Buildings: Unlike the "Stay Put" strategy, which is more suited to certain types of buildings (like high-rise residential buildings with fire-resistant compartmentation), the "Simultaneous Evacuation" strategy can be applied more universally. This is particularly true for buildings equipped with the aforementioned safety features. It's a strategy that assumes all occupants can and should evacuate the building immediately upon the detection of a fire.

4. General Safety and Efficiency: This strategy is beneficial in scenarios where immediate evacuation is necessary, and the building's design supports the safe and efficient movement of all occupants. Buildings with multiple and accessible escape routes, clear signage, and emergency lighting are better suited for this approach.

5. Requires Comprehensive Fire Safety Planning: Implementing a "Simultaneous Evacuation" strategy requires thorough planning and regular drills. Occupants need to be familiar with evacuation routes and procedures. Additionally, the building management must ensure that safety systems are regularly inspected and maintained.

In summary, the "Simultaneous Evacuation" strategy is a proactive approach to fire safety, relying on the immediate and orderly evacuation of all occupants. It's most effective in buildings equipped with advanced fire safety systems that keep escape routes free of smoke, allowing for a swift and organized exit during an emergency. This strategy emphasizes the importance of preparation, clear communication, and regular practice of evacuation procedures.

Q(Eam Taekyoung) : On the other hand, in a building where the influence of the stack effect in winter must be considered, if a pressurization system is applied that only pressurizes the vestibule adjacent to the staircase or the lobby adjacent to the hoistway and does not directly pressurize the staircase or the hoistway, it may not be possible to prevent the spread of fire room smoke to other floors due to the stack effect.

Therefore, it appears that a simultaneous evacuation strategy should be used only when the pressurization system can reliably prevent smoke from penetrating the escape route due to the stack effect.

A(ChatGPT 4) : Your understanding of the challenges posed by the stack effect in high-rise buildings during winter, and its impact on fire safety strategies, is quite accurate. The stack effect, which is the movement of air into and out of buildings driven by indoor-outdoor temperature differences, can significantly influence the behavior of smoke during a fire. Let's delve into how this affects the use of a simultaneous evacuation strategy:

1. Stack Effect in Winter: In winter, the stack effect is typically more pronounced in tall buildings due to the greater temperature difference between the heated interior and the cold exterior. Warm air rises to the top of the building, creating a lower pressure at the bottom, which can draw in cold air. During a fire, this effect can cause smoke to spread more rapidly and unpredictably, especially through vertical shafts like staircases and elevator hoistways.

2. Challenges with Partial Pressurization: When a pressurization system only targets specific areas like vestibules or lobbies and does not directly pressurize the staircases or hoistways, it may not effectively counteract the stack effect. This can allow smoke to infiltrate these critical escape routes, compromising their safety and the viability of a simultaneous evacuation strategy.

3. Need for Comprehensive Pressurization Systems: For a simultaneous evacuation strategy to be effective, especially in buildings where the stack effect is significant, the pressurization system must be robust enough to prevent smoke from entering escape routes. This means direct pressurization of stairwells and hoistways to create a positive pressure barrier that resists the infiltration of smoke, countering the stack effect.

4. Assessing the Efficacy of Pressurization Systems: It's crucial that the effectiveness of these pressurization systems is regularly tested, particularly in consideration of seasonal variations like the stack effect in winter. Building management should conduct thorough assessments to ensure that the systems can reliably maintain smoke-free escape routes under various conditions.

5. Adapting Evacuation Strategies Accordingly: If a building's pressurization system cannot effectively counteract the stack effect, then relying solely on a simultaneous evacuation strategy may not be advisable. Alternative strategies or additional safety measures might be needed to ensure the safe evacuation of occupants.

In summary, the success of a simultaneous evacuation strategy in tall buildings during winter heavily depends on the effectiveness of the building's smoke control systems, especially in mitigating the impact of the stack effect. Regular assessment and maintenance of these systems are essential to ensure they function as intended in all conditions, providing a safe environment for occupants to evacuate promptly in the event of a fire.