NIST/Simulation of a Fire in a Hillside Residential Structure San Francisco, CA

sffd_logoBuildingsonfire Lessons from the Fireground – NIST/Simulation of a Fire in a Hillside Residential Structure San Francisco, CA

On June 2, 2011, a fire in a multi-level, wood-frame residential structure claimed the life of two firefighters of the San Francisco (CA) Fire Department. NIST examined the fire dynamics of this incident at the request of the National Institute for Occupational Safety and Health (NIOSH) and the San Francisco Fire Department. A computer simulation of the fire incident was conducted using Fire Dynamics Simulator and Smokeview to provide insight into the fire development and thermal conditions that likely existed in the residence during the fire.

NIST Report HERE

NIST Simulation Video HERE

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The specific objectives of the simulation detailed in this report are:

  1. To examine the effect of fire-induced flow paths (including temperature, pressure, and fire conditions) in this multi-level residential structure using physics-based calculations.
  2. To provide visualizations of the fire behavior that are representative of the conditions that members of the San Francisco Fire Department likely experienced during the course of their interior operations.

The report issued describes the input and the results of the FDS (version 6.1.2) simulation. The simulation was developed using a combination of knowledge of the fire scenario and appropriate engineering approximations and assumptions. Analysis of the simulation results focuses on the hazardous conditions that developed following the development of a flow path inside of the structure.

The NIST report is organized as follows:

  • Section 2 provides a summary of the fire incident,
  • Section 3 describes the relevant model input parameters and assumptions that were used to develop the simulation,
  • Section 4 presents the simulation results, and
  • Section 5 discusses the simulation results as they relate to firefighter safety and effectiveness.
  • Appendix A contains dimensioned drawings of the basement, first, and second floors of the structure.

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On the morning of June 02, 2011, the San Francisco Fire Department was dispatched to a residence based on a report of curtains on fire. The account of events for this incident was documented in NIOSH Fire Fighter Fatality Investigation and Prevention Program Report #F2011-13

On June 02, 2011, a 48 year-old career lieutenant and a 53 year-old fire fighter/paramedic died in a multi-level residential structure fire while searching for the seat of the fire. Note: The residential structure where the fatalities occurred was built on a significantly sloped hillside common throughout the city. The fire floor was one floor below street level. Six companies and three command chiefs were dispatched to a report of an electrical fire at a residential home.

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When Engine 26, staffed with a lieutenant, fire fighter/paramedic, and driver arrived at approximately 1048 hours, they noticed light smoke showing as they made entry through the front door, side A, street level, of the building. Minutes later, the incident commander (IC) tried contacting them over the radio, but received no response. A battalion chief (BC) assigned to “the fire attack group” followed the hoseline through the door and spoke to the [lieutenant and fire fighter/paramedic] on the street level floor. The lieutenant stated to the BC that the fire must be a floor below them. The BC stated they would attack the fire from the [left side] of the structure and exited the front door. The [lieutenant and fire fighter/paramedic] did not follow. A few minutes later the IC again tried to contact Engine 26 via radio with no response.

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Executive Summary

Fire Dynamics Simulator was used to provide insight into the fire dynamics of a fire that occurred within a multi-level, single-family residential structure in San Francisco, CA, that resulted in the death of two firefighters. The fuel, fire size, and fire growth rate that were used in the FDS simulation were estimated by taking into account all of the available information including the NIOSH report, post-incident pictures, and relevant literature.

  • This resulted in a maximum specified source fire of approximately 20 MW in the basement and rear balcony of the structure.
  • Based on the limited ventilation conditions in the basement, the FDS simulation results indicated a HRR of approximately 2 MW as a result of the limited supply of oxygen.
  • After the rear basement windows failed, the HRR increased to approximately 32 MW before it reached a steady-state value of approximately 20 MW.

The fire originated in the basement, and the interior stairwell acted as a chimney for hot gases in the basement to flow towards regions of lower pressure and vent openings located on the front side of the structure. After the rear basement windows failed, a flow path was established between the basement living room area and the doors located on the front side of the structure (the front door and the garage door).

  • The rear basement window failures resulted in a rapid change in the conditions within the flow path.
  • In the interior stairwell, the flow velocities were approximately 9 m/s (20 mph) and the temperature of the gases was estimated to be in excess of 700 â—¦C (1300 â—¦F), which exceeds the Class III exposure temperature of 260 â—¦C (500 â—¦F).

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Two firefighters were located in the flow path between the basement and the doors on the front side of the structure. After a call for assistance, both firefighters were removed from the structure and immediate medical treatment was provided.

The two firefighters were transported to the local medical center where the lieutenant was pronounced dead and the fire fighter/paramedic died two days

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NIST Simulation Video

From Table 5.1 of the report for listing of Flow path related LODD/LODI

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Report Cover