A Quick Guide for Adding Sprinklers to Historic Structures

Historic designation, by its name alone, implies, at the least, that a designer is going to approach such a project differently from a typical project. In the state of Florida, historic designation also means the particular facility is protected by local and state historic regulatory agencies from requirements of building and zoning rules that may alter its appearance.

10/01/2004


Historic designation, by its name alone, implies, at the least, that a designer is going to approach such a project differently from a typical project. In the state of Florida, historic designation also means the particular facility is protected by local and state historic regulatory agencies from requirements of building and zoning rules that may alter its appearance. Adding sprinklers, clearly, will alter appearances. But such structures still require fire-protection and life-safety systems to meet the intent of state and local statutes. For example, Florida requires automatic sprinklers in all non-historic hotels three stories and higher. Here are a few factors to consider when trying to achieve the right balance between preservation and safety:

  1. Develop realistic fire scenarios, defined in terms of fire size and heat release rate and based upon the combustible loading available.

  2. Determine the rate of smoke mass production and associated smoke layer height with respect to time for each fire scenario.

  3. Determine the anticipated occupant loads based upon floor areas and occupant load factors from NFPA 101.

  4. Evaluate egress times based upon the calculated occupant load and proposed egress paths, including appropriate safety factors.

  5. Compare the smoke layer heights with egress times for each scenario.

As a way to determine the nature of an existing facility, a timed egress and smoke production analysis allows engineers to evaluate the level of life safety provided in these selected areas of an existing building. One way to do so is to compare calculated egress times to smoke layer heights for specific fire sizes.

Quantification of anticipated smoke production rates and associated smoke layer heights can be accomplished by conducting an analysis in accordance with established principles of engineering and NFPA 92B.

The amount of smoke produced for each fire scenario can be determined by the room configuration. The general steps include:

  1. Calculation of the mass flow rate at incremental time steps.

  2. Conversion of the mass flow rate to a volumetric flow rate during each time step.

  3. Calculation of the cumulative sum of the volumetric flow rates determined in Step 2 for all time steps. This yields the total volume of smoke within the compartment at a given time.

  4. Calculation of the layer height from the total volume of smoke based upon the area and height of the ceiling.

Finally, consider time of egress. The exit analysis provided by Dr. John Fruin in his "Pedestrian Planning and Design" and several articles by Jake Pauls of the National Research Council of Canada serve as excellent resources. A description of the analysis process is given in Chapter 3%%MDASSML%%13 of the SFPE Handbook of Fire Protection Engineering (Second Edition - 1995).



Sprinkler considerations

Develop realistic fire scenarios

Determine smoke mass production

Determine occupant loads

Evaluate egress times

Compare egress time to smoke layer height



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