What Is Fire & Egress Modeling? [QUICK GUIDE]

Our team of experts offers regular updates on FPE and life safety best practices, code modifications and more.

Aric Aumond, P.E.


October 5, 2023

Numerous factors play into a building's design, and fire safety is among the most important. Luckily, fire and egress modeling make predicting fire and occupant behavior possible, leading to increased fire safety. But what are these applications, and how do they work?

What Is Fire Modeling?

Fire modeling is a computational technique used to simulate and predict the behavior of fires in various environments. It involves the application of mathematical equations and computer algorithms to replicate the complex physical and chemical processes that occur during a fire. 

Fire modeling serves multiple purposes, including fire safety engineering, firefighting strategy development and assessing the potential impact of fires on structures and the environment. 

These models consider factors such as:

  • Fuel type
  • Fire spread 
  • Heat release rates
  • Smoke production
  • Weather conditions

Fire protection engineers use fire modeling to analyze fire scenarios, optimize evacuation plans and design fire-resistant structures, ultimately contributing to enhanced fire safety measures and the mitigation of fire-related risks. It plays a crucial role in ensuring public safety and safeguarding against the destructive forces of fires.

What Is Egress Modeling?

Egress modeling is a specialized field within the realm of architectural and fire safety engineering that focuses on simulating and analyzing the movement of people during emergencies, particularly evacuations from buildings or confined spaces.

This practice utilizes mathematical models and computer simulations to predict and optimize the flow of occupants as they exit a structure or navigate through it during a crisis, such as a fire.

Egress models take into account factors like:

  • Building layout
  • Occupant behavior and movement speeds
  • Exit locations
  • Signage
  • The capacity of pathways and exits
  • The impact of hazardous smoke 

By using this data, egress modeling helps to design buildings and spaces that are better equipped to handle evacuations efficiently and safely. It also aids in evaluating and refining evacuation plans, identifying potential bottlenecks or hazards and ensuring compliance with safety regulations.

As a result, egress modeling plays a vital role in enhancing the safety and survivability of occupants during emergency situations.

How Do Fire & Egress Modeling Work Together?

Fire modeling and egress modeling work closely to improve fire safety and evacuation strategies in buildings. Fire models assess potential hazards and conditions evacuees might encounter, such as smoke and heat. Egress models, in turn, consider the influence of these factors on occupant behavior and movement, helping to optimize escape routes, exit placements and emergency signage.

This collaborative approach allows architects, engineers and safety professionals to design buildings that facilitate safe and efficient evacuations during fires and other emergencies, ultimately saving lives and minimizing property damage.

ASET vs. RSET Analysis

ASET vs. RSET is the fundamental technical basis for most fire and egress modeling approaches, which ensures buildings are well-prepared to protect occupants during fire emergencies.

ASET (Available Safe Egress Time) is the time occupants can remain safely inside a building before being exposed to hazardous conditions, such as heat, smoke or toxic gases. ASET is quantified based on the failure of any of the following performance criteria:

  • Visibility distance 
  • Temperature thresholds
  • Carbon monoxide concentrations

RSET (Required Safe Egress Time) is the time it takes for all building occupants to safely evacuate the premises. It is largely impacted by the type of occupancy, number of occupants, building exit layout and the expected behavior of people during an emergency. ASET is comprised of the following segments:

  •  Alarm and occupant notification time
  • Premovement time (evacuation delay)
  • Movement time

An ASET vs. RSET analysis begins with fire modeling, where simulations are used to predict the development and spread of a fire within a building (ASET). Concurrently, egress modeling simulates how occupants will evacuate during an emergency (RSET). The key objective is to ensure that ASET exceeds or at least equals RSET, ensuring a margin of safety for occupants. If ASET falls short of RSET, it signals the need for potential improvements in fire protection systems, additional exits or changes in evacuation protocols to enhance occupant safety.

What Software Is Used for Fire & Egress Modeling?

There are various kinds of software applications available for fire and egress modeling. Each is intended for specific applications and has limitations. Let’s explore some of the most popular options.

Fire Modeling Software

  • FDS (Fire Dynamics Simulator): A computational fluid dynamics software used to simulate the behavior of fires and smoke in buildings and other environments.
  • CFAST (Consolidated Fire and Smoke Transport): A software tool for modeling the spread of fires and smoke in buildings, assisting in fire safety and evacuation analysis.
  • PyroSim: A graphical user interface for the FDS software, designed to facilitate the creation, simulation and analysis of fire scenarios in buildings and other structures.

Egress Modeling Software

  • Pathfinder: A computer-based software program used for simulating human movement and evacuation in buildings during emergency situations, helping to optimize safety and egress planning.
  • Simulex: A computer software tool used for simulating and analyzing the evacuation and movement of people in buildings during emergency situations, aiding in the assessment of evacuation strategies and safety measures
  • STEPS (Simulation of Transient Evacuation and Pedestrian Movements): A computer-based simulation software used for modeling and analyzing the dynamics of pedestrian movement and evacuations in various environments, helping to enhance safety and crowd management.

Who Should You Hire for Fire & Egress Modeling?

When you want a fire and egress modeling expert for your project, it’s important to remember not all fire protection engineers (FPEs) are created equal. Since fire and egress modeling is a specialized field of fire protection engineering, only a few companies can support this complex service. Therefore, you should work with an FPE that has the following qualifications to ensure success:

  1. Expertise in fire dynamics
  2. Safety focus
  3. Code compliance
  4. AHJ negotiations 

1. Expertise in Fire Dynamics

Specialized FPEs have knowledge of fire behavior, combustion, and heat transfer – both academic and real world. Fire department response operations have a significant impact on fire development and protection strategies. They use this knowledge to understand the intricacies of fire modeling and can accurately simulate how fires develop and spread within a building. 

2. Safety Focus

The right FPE will prioritize safety. They’re formally trained to identify fire hazards, assess risks and design fire protection systems to mitigate potential dangers. This safety-conscious mindset is invaluable when conducting fire and egress modeling and limiting potential risks and liabilities.

3. Code Compliance

It’s essential for any fire and egress modeling specialist to be well-versed in building codes, fire safety standards and regulations. Choose an expert FPE that fits the bill, as they can ensure your modeling efforts align with local, national and international fire safety codes.

4. AHJ Negotiations 

As much as fire and egress modeling projects are a technical science, they are also a political science. The success of fire and egress modeling projects depends on communication with building and fire code officials; often educating them on the progression of technologies and industry-accepted methodologies. 


Fire and egress modeling are essential tools for understanding, assessing and enhancing the safety of buildings and environments. These modeling techniques, when leveraged by qualified professionals, are indispensable in the quest for fire safety, and they ultimately save lives and reduce property damage in the event of a fire.

Performance Based Fire Protection Engineering uses cutting-edge technology to perform fire and egress modeling for high-rises, warehouses and other types of buildings. Contact us to learn more about how we can help keep your building – and occupants – safe.