Characterizing Fire Safety in Residential Buildings with Single Exit Stairs Using Fire Dynamics Simulator (FDS)

As discussions around housing affordability and urban development continue to evolve, municipalities and building professionals are reconsidering long-standing design constraints. One such topic gaining traction is the use of single-exit stair designs in residential mid-rise buildings. While single-stair buildings aim to reduce construction costs and utilize tight lot sizes in urban environments, the overall impact on occupant safety and firefighter operations necessitates more insight.

At Performance Based Fire Protection Engineering (PBFPE), now a part of Summit Fire Consulting, advanced fire modeling techniques are being applied to address emerging challenges in fire protection. Rachel Kirk, a fire protection engineer at PBFPE, is leveraging the technical capabilities she has developed through her work in fire modeling and performance-based design to conduct master's research at Worcester Polytechnic Institute (WPI). Her independent study analyzes the fire safety performance of residential buildings with single-exit stair configurations using Fire Dynamics Simulator (FDS). The goal of this study is to provide quantitative data that can contribute to a more informed discussion on this topic. 

Research Overview

Rachel has created model buildings for a comparative analysis, focusing on six-story residential structures with different stair configurations as well as fire protection and life safety measures. These models allow for a detailed examination of tenability conditions under various fire scenarios. The study compares two primary stair layouts:

• Single-stair design with one centrally located stairwell.
• Two-stair design with stairwells positioned at opposite ends of a corridor.

To assess fire safety performance, multiple fire scenarios will be simulated in FDS, analyzing smoke spread, visibility, temperature, and species production at key locations throughout the buildings. Key factors considered in the study include:

• The presence or absence of automatic sprinkler protection: Some scenarios will include sprinklers to assess the impact of different-sized fires on smoke spread.
• Stair door position and leakage pathways: Examining how smoke migration varies depending on whether doors remain open or closed to stairways, or said doors are failed to be maintained.
• Stairwell pressurization and environmental conditions: Evaluating how the smoke control system may influence smoke spread and tenability.

Objectives & Key Findings

The primary objective of Rachel’s research is to generate a matrix of fire scenarios that offer quantitative insights into key life safety features in single- and two-exit stair buildings. By analyzing how different factors influence tenability, this study aims to provide data that can support informed decision-making regarding building codes and design practices. Some of the areas under examination include:

• The differences in smoke migration and occupant tenability between single- and two-stair designs.
• The effectiveness of active fire protection systems, such as sprinkler systems and stairwell pressurization, in mitigating fire hazards.

This study seeks to provide a technical analysis that can contribute to ongoing discussions within the fire protection community. The results will be compiled into a forthcoming white paper, which will be available as a reference for engineers, code officials, and policymakers.

Advancing Fire Protection Research

Applying rigorous technical analysis to evaluate new design strategies is essential in fire protection engineering. By leveraging fire modeling tools such as FDS, valuable data can be generated to guide code development and ensure occupant safety in evolving building designs.

Through Rachel’s research at WPI and her collaboration with PBFPE, innovative fire protection solutions that balance safety, efficiency, and practicality will continue to be explored. Rachel was recently selected to present her findings at the SFPE conference in Vancouver this fall. Additionally, the full white paper will be released upon completion of the study, providing detailed findings and insights on this subject.

If you need expert FDS modeling for your project, PBFPE can help. Contact us to discuss your needs with one of our fire protection engineers.