Fractional Effective Dose Integration with Evacuation Results

Reading Time: 3 minutes
Created with software version: 2020.1

1. Introduction

Fractional Effective Dose (FED) is a measure of airborne contaminants absorbed by an occupant. Hazards such as carbon monoxide and carbon dioxide are accumulated during the occupant’s movement through a burning building. Pathfinder records Plot3D quantities from FDS output such as species volume fraction, soot visibility, and temperature.

If carbon dioxide, carbon monoxide, and oxygen volume fractions are given, Pathfinder will calculate additional FED output. All recorded Plot3D data is stored in the Additional Print Data for each individual occupant. Note that these values have no impact on movement, and the processing required to integrate FDS output data can have a substantial impact on simulation performance.

excel scrn fed output
Figure 1. Example Fractional Effective Dose output at a one second interval for a single occupant

This functionality bridges Pathfinder and PyroSim to bring a new way to analyze performance data. Providing FED calculations enhances the confidence of a fire safety risk assessment. A practical FED tool has become necessary as more authorities inquire about contaminant data.

2. Instructions

To prepare a Smokeview file (*.smv) for FED output, it must contain specific Plot3D data. Use PyroSim to enable Write Plot3D XYZ File on the Output tab of the Simulation Parameters dialog box. Set a Plot3D Write Interval of about 5.0 seconds to continually update the information in the file. Alternatively, you can edit your FDS file by setting WRITE_XYZ to TRUE and setting a time interval value for DT_PL3D.

Select Plot3D data on the Output menu to open the Plot 3D Static Data Dumps dialog box. FDS will only allow up to five quantities to be calculated in a single simulation. The following quantities are necessary for Pathfinder to calculate FED.

  • \(CO\) Volume Fraction
  • CO2 Volume Fraction
  • O2 Volume Fraction

Once the fire simulation has completed, Pathfinder can access FDS results data. To load FDS data in Pathfinder, select the Smokeview file that you want to import from the FDS Data tab on the Simulation Parameters dialog box. The file will be analyzed for the proper Plot3D outputs quantities.

path ui dialog simulation parameters
Figure 2. Importing a Smokeview file into Pathfinder for Fractional Effective Dose output

With the *.smv file imported, select which occupants to compute FED data for. Select one or more occupants and then click the More button to open the Additional Occupant Properties dialog box. On the Output tab, select Print CSV Data and change the value to Yes to override the setting from the occupant’s profile.

Once the simulation has completed, a new occupant *.csv file appear in the output directory. For more information on how FED is calculated or how its use was verified in Pathfinder, see the Pathfinder Technical Reference Manual and Pathfinder Verification and Validation documents respectively.

To download the most recent version of Pathfinder, please visit the Pathfinder Support page and click the link for the current release. If you have any questions, please contact

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