Improving fire investigators’ understanding of fire patterns by increasing knowledge of fire behavior and the impact of ventilation on different fire scenarios

Knowledge of fire dynamics is critical for fire investigators to properly identify a fire’s origin. Fire dynamics depend on the relationship of the fuel, heat, and ventilation during a fire event. A ventilation change as simple as a door left open by an occupant fleeing the fire, a window open remote from the fire, or a window that fails as a result of fire growth could greatly impact the fire damage inside the structure. 

Key objectives: 

1. Improve investigators’ understanding of fire patterns by increasing knowledge of fire behavior and the impact of ventilation on different fire scenarios
2. Develop knowledge of fire patterns within full-size modern residential homes, incorporating an open floor plan and two-story great room
3. Identify and disseminate standard best practices for the use of fire damage and patterns resulting from ventilation during fire based on science
4. Conduct fire modeling based on a series of full-scale fire experiments to further the linkage between modeling, fire ventilation and fire patterns

Full-scale testing was performed in representative models of modern single-family homes that incorporated modern construction practices.

Here’s why: over the past 30 years, home construction materials, contents, size and geometry have changed drastically—and consequently, so has fire behavior. Today’s fires, thriving as they do on predominantly synthetic materials, tend to become ventilation-limited. How and where a fire receives oxygen greatly impacts the fire dynamics and subsequent fire patterns.

Researchers performed three types of full-scale experiments over 40 days at UL’s Large Fire Lab in Northrbook, Illinois including:

1. Ranch house (1200 sq. ft. single family, ranch-style house) experiments ranged from fires with no exterior ventilation, to room fires with flow paths that connected the fires with remote intake and exhaust vents throughout the structures. Elevated fires originating in a kitchen were also examined.
2. Colonial house (3200 sq. ft. two-story colonial style house) experiments ranged from fires with no exterior ventilation, to room fires with flow paths that connected the fires with remote intake and exhaust vents throughout the structures. Elevated fires originating in a kitchen were also examined.
3. Exposed electrical cord and cable experiments were designed to compare the thermal conditions that lead to failure of different energized cord and cable systems and the type of trip for different circuit breakers when exposed to flashover conditions. Eighteen configurations which consisted of 6 different cords and cables and 3 circuit breakers for each cord/cable type were installed in the floor at the ventilation opening.

 

Impact of Ventilation on Fire Patterns from UL FSRI on Vimeo.

 

Relevant Resources

RESOURCE #1: Impact of Ventilation on Fire Patterns Project Page

RESOURCE #2: Fire Investigation Data Portal

RESOURCE #3: Impact of Flashover Fire Conditions on Exposed Energized Electrical Cords and Cables Report

RESOURCE #4: Impact of Fixed Ventilation Fire Damage Patterns in Full-Scale Structures Report

RESOURCE #5: Introduction to Heat Transfer and Fire Measurement Online Course