Impact of Natural and Mechanical Ventilation on Fire Patterns in a Residential Structure

Overview

Through full-scale experiments, the Fire Safety Research Institute (FSRI), part of UL Research Institutes examines fire patterns and fire behavior from changes in natural ventilation or the presence of mechanical ventilation from an HVAC system. 

This study builds on FSRI’s previous fire pattern research supported by NIJ Grant Award  2015-DN-BX-K052. The previous work studied the repeatability of the fire dynamics, repeatability of fire patterns, and post-flashover persistence of a fire pattern in the area of origin. In that study, the door and window openings were controlled to eliminate the opportunity for the ventilation to change during the development of the fire. When the doors and window openings were closed, the fires were shown to self-extinguish due to a lack of oxygen within the structure. When a doorway or a window was opened prior to ignition, the fires had an adequate oxygen supply to transition through flashover and sustain burning. This study examines the impact of a passive HVAC system and changes in ventilation during the fire through a series of structure fires that were conducted for the Study of Fire Service Residential Home Size-Up and Search & Rescue Operations. 

Context

Changes in home construction materials, insulation, and contents demonstrate the importance of understanding how ventilation affects fire behavior. In today’s fire environment, fires in rooms predominantly composed of synthetic contents, often become ventilation-limited. How and where the fire receives oxygen greatly impacts the fire dynamics and subsequent fire patterns. 

Objectives

• Examine changes to fire patterns resulting from changes to ventilation during the course of a fire in a ranch style home.  
• Examine changes to fire effects and patterns as the result of ventilation from an operating  residential HVAC system.