Nathan D. Marsh

Analyzing smoke alarm response to flaming fires using the fire model JET

An algorithm that calculates the time dependent smoke concentration in a fire-induced ceiling jet within a smoke layer and algorithms for predicting the response of photoelectric smoke alarms, both of which are part of the computer model JET, are examined using three different fires in a small room. The objectives of this analysis are to test the ceiling jet smoke algorithm and understand the limitations of analyzing signals from photoelectric smoke alarms located in the ceiling jet to estimate fire size and thereby support decision making by emergency responders. The analysis is restricted to flaming fires that produce turbulent plumes and can be represented by axisymmetric point sources. Two different smoke yields from the literature are used to obtain ceiling jet smoke density from JET. Depending on the value of the smoke yield used, the predictions of JET follow or do not follow the photoelectric smoke alarm signals. This suggests that additional information about how smoke yields are measured or that a better calibration technique is required in order to accurately model smoke alarm response.

Understanding the Hazards of Grouped Electrical Cables

CHRISTIFIRE (Cable Heat Release, Ignition, and Spread in Tray Installations during FIRE) is a U.S. Nuclear Regulatory Commission Office of Research program to quantify the mass and energy released from burning electrical cables. This type of quantitative information will be used to develop more realistic models of cable fires for use in fire probabilistic risk assessment (PRA) analyses. The experimental program has two main thrusts—bench-scale measurements of small samples of burning cables and full-scale measurements of the heat release and fire-spread rates of cables burning within typical ladder-type trays. The bench-scale measurements include micro-calorimetry of cable components, effluent characterization using absorption spectroscopy, and measurements of the heat release rate using a cone calorimeter. The full-scale measurements include the burning of a variety of cables within a typical tray under radiant panel heating, and full-scale, multiple tray fires. The outcome of the experiments is to be used by a variety of fire models, ranging from simple correlations to computational fluid dynamics.

Sensitivity of a Smoke Toxicity Test Method to Test Conditions

Experiments have been conducted in the NFPA 269 / ASTM E1678 radiant apparatus to determine the sensitivity of toxic gas generation to atmospheric oxygen availability and to the conformation of the test specimen. CO and HCN generation can be dependent on the conformation of the test specimen. Thus, it is important that the test specimen exposure to the radiant source adhere to the likely real-fire exposure of the finished goods. Reducing the initial oxygen volume fraction in the apparatus can affect CO and HCN generation, but does not appear to affect the HCl generation. Fitting the bench-scale test conditions to the full-scale fire ventilation conditions is likely to be important in obtaining good correlations of toxic gas generation.