E Braun

Toxicological interactions between carbon monoxide and carbon dioxide

Fischer 344 male rats were subjected to 30-min individual or combined exposures of carbon monoxide (CO) and carbon dioxide (CO2). All deaths from CO occurred during the exposures, and the LC50 values were 4600 and 5000 ppm, depending on experimental conditions. Animals exposed to CO2 concentrations ranging from 1.3 to 14.7% for 30 min were neither incapacitated nor fatally injured. The addition of nonlethal concentrations of CO2 (1.7 to 17.3%) to sublethal concentrations of CO (2500 to 4000 ppm) caused deaths of the exposed rats both during and following (up to 24 h) the 30-min exposures. The most toxic combination of these two gases (2500 ppm CO plus 5% CO2) increased the rate of carboxyhemoglobin (COHb) formation 1.5 times that found in rats exposed to 2500 ppm of CO alone. The COHb equilibrium levels were the same. Exposure to both CO and CO2 produced a greater degree of acidosis and a longer recovery time than that observed with either single gas. The results fit a mathematical model indicating a synergistic interaction. Combustion of 11 materials at their LC50 values indicated that CO was probably the primary toxicant in one case and that the combined CO plus CO2 was the cause of the deaths in three other cases. Additional fire gases need to be studied to explain deaths from the other materials.

Large-Scale Validation of Bench Scale Fire Toxicity Tests

A sizable number of bench-scale fire toxicity tests have been pro posed over the last two decades. To date, no test method has successfully passed through the standards bodies ISO, ASTM, or BSI. The reasons are varied, but a major concern has been that none of the methods were seen to adequately pre dict the behavior of real, large-scale building fires. Such validation efforts have been held back both due to a shortage of good quality data, and because agree ment had not been reached on the criteria for successful validation. NIST has now completed a pilot project to address both of these issues. In this study, sev eral criteria for validation have been put forth. An initial data set has been compared against these criteria, comprising 2 bench-scale methods, 3 test materials, and a single real-scale fire scenario. The project results indicate that the course being pursued is appropriate, and provide illustrative performance data for the two bench-scale methods. The present project was a pilot study; fur ther validation data will have to come from additional test materials and addi tional real-scale fire scenarios being examined. As a result of these studies, a factor-of-3 agreement between bench-scale and real-scale results was estab lished as both useful and practical.

Fire Performance of an Interstitial Space Construction System (NISTIR 5560)

A 2000-CHARACTER OR LESS FACTUAL SUMMARY OF MOST SIGNIFICANT INFORMATION. IF DOCUMENT INCLUDES A SIGNIFICANT BIBLIOGRAPHY OF LITERATURE SURVEY. CITE IT HERE. SPELL OUT ACRONYMS ON FIRST REFERENCE.) (CONTINUE ON SEPARATE PAGE, IF NECESSARY.) A interstitial space building construction assembly conaistiugof a walk-on deck suspendedfrom above by structural steel which alsc supported a functional floor, reproduce a design planned for use in a new hospital complex at Elmendorf Air Force Base, Alaska. This interstitial space assembly was built in the multi-story steel test structure at the National Institute of Standards and Technology The constructionassemblywas tested by the sameprotocol used to evaluatethe Veterans’Administration interstitial spaceconstructio~ assembly, tested in 1984. This protocol followed the National Fire Protection Association’s NFPA 251 Fire Tests of Buildinf Constructionand Materials Standard, 1990 edhion. Fire testing of the interstitirdspace system was carried out during the summer oj 1994. This construction assemblymet the requirementsfor a 2 hour fire endurancerating. The maximum surface temperatureon tht unexposed functional floor above the interstitial space reached 33 ‘C (91 “F) at the end of the two hour period. The maximun structural steel temperature inside the interstitial space was 123 “C (253 “F). The structural assembly was evaluated for a total of; hours and 30 minutes before the test was terminated.

An Assessment Methodology For The Fire Performance Of School Bus Interior Components

A full-scale fire performance protocol for the evaluation of school bus seat assemblies was developed. This protocol is based on the results of full-scale testing of end-use seat assemblies and computer fire modeling of the ignition source and burning item(s) in a single compartment enclosure. Tenability criteria were applied to the results of the full-scale tests and computer fire model calculations. The results showed that temperature is a suitable criterion for this application. Toxicity of the decomposition products plays a secondary role in determining occupant survivability. Occupant tenability limits are exceeded for ignition sources over 300 kW, independent of the type of seat assembly. Based on the full-scale test data, computer simulations were conducted to determine which tenability criteria were exceeded in the full-scale tests.