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CFAST Fire Modeling

Priest & Associates Consulting is now offering CFAST Fire Modeling.

Excerpts from CFAST:

CFAST is designed primarily to predict the environment within compartmented structures which results from unwanted fires. These can range from very small containment vessels, on the order of 1 m3 to large spaces on the order of 1000 m3. The appropriate size fire for a given application depends on the size of the compartment being modeled.

CFAST has been subjected to extensive use and review both internal to NIST and by users worldwide in a broad range of applications. In addition to review within NIST independent of the model developers, the model has been published in international peer-reviewed journals worldwide, and in industry-standard handbooks referenced in specific consensus standards. Besides formal internal and peer review, CFAST is subjected to continuous scrutiny because it is available to the general public and is used internationally by those involved in fire safety design and post-fire reconstruction.

Many of the outputs from the CFAST model are relatively insensitive to uncertainty in the inputs for a broad range of scenarios. Not surprisingly, the heat release rate is the most important variable because it provides the driving force for firedriven flows. For CFAST, the heat release rate is prescribed by the user. Thus, careful selection of the fire size is necessary for accurate predictions.

The CFAST model has been subjected to extensive validation studies by NIST and others. Although some differences between the model and the experiments were evident in these studies, they are typically explained by limitations of the model and uncertainty of the experiments. Most prominent in the studies reviewed was the overprediction of gas temperature often attributed to uncertainty in soot production and radiative fraction.

Still, studies typically show predictions accurate within about 30 % of measurements for a range of scenarios. Like all predictive models, the best predictions come with a clear understanding of the limitations of the model and of the inputs provided to the calculations. CFAST has been developed for use in solving practical fire problems in fire protection engineering. It is intended for use in system modeling of building and building components. A priori prediction of flame spread or fire growth on objects is not modeled. Rather, the consequences of a specified fire is estimated.

Priest and Associates has used CFAST to predict the results of actual tests and extended the model to larger volume compartments for real scale analysis. The large volume predictions agreed with predictions using other techniques with reasonable accuracy.

If you need to know the properties of a room or compartment based on a known fire curve, we can model the scenario and provide predictions of room temperatures, heat flux, oxygen starved heat release rates, and other properties which can be used for further analysis such as the propensity to ignite nearby objects and other fire response parameters.

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