An operator independent method for measuring the time to ignition is presented. Ignition occurs when the 2 nd derivative of mass loss vs. time curve reaches its peak, i.e., when the mass loss rate increases most rapidly due to applied heating. Prior to evaluating the 2 nd derivative one smoothes the data using the 4 th order Savitski-Golay method. The technique is demonstrated for a wide variety of polymers (PMMA, POM, FRPP, Polyisocyanurate foam, PVC, CPVC and PVDF) to examine their ignition behavior in ambient air as well as in 40% oxygen. The 2 nd derivative and the observed ignition times are compared. In all cases, the times are identical in 40% oxygen. The two times are also identical for ordinary polymers in air. However, for the halogenated fuels, PVC, CPVC and PVDF, the observed ignition is both intermittent and delayed. For halogenated fuels, enhanced ambient oxygen accelerates gas-phase combustion, but has negligible effect on initiation of mass transfer. In most cases, the agreement between observed and 2 nd derivative ignition times in air and in 40% oxygen is quite remarkable, confirming that the operator independent 2 nd derivative ignition method is both reliable and consistent.

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Background: Naturally occurring radioactivity is a root cause of human exposure to harmful radiation. The occupational exposure hazard due to natural radionuclides occurring in drilling wastes is especially important in this regard. In this study the concentration of radionuclides namely 232 Th, 226 Ra and 40 K were assessed in soil samples that were taken from various oil drilling areas. Methodology: 10 samples were collected and sealed for two months to ensure the secular equilibrium between 226 Ra and 232 Th, and their respective radioactive progenies. The concentration of radionuclides in samples was measured by gamma spectroscopy. Descriptive and analytical statistics were used in order to analyze the data. Results: the results showed the average absorbed dose rates (D), annual effective dose (AED), Radium equivalent activity (Raeq) and various hazard indexes(Hex, Hin and Iγ ) for samples were 38.22 nGy/h, 0.046 mSv/y, 81.032 Bq/Kg, 0.21, 0.31 and 0.59, respectively. Conclusions: The mean activity concentrations were lower than the world mean values, according to the radiation protection criteria that identified by UNSCEAR.