The outcomes of binary collisions of water droplets are investigated experimentally for the range of parameters of a spray system used during a severe nuclear reactor accident. Droplets diameters range from 220 to 450 m with a diameter ratio between 0.5 and 1 and impact velocities between 3 and 10 m s −1 . Values of the Weber number based on the small droplet size are between 20 and 280. For droplets with a Weber number up to 120, results in a map of impact parameters versus Weber number show the various regimes, namely, stretching separation, coalescence and reflexive separation. For a higher Weber number, between 120 and 280, the only observed outcomes are the two separation regimes. It is shown that results obtained for unequal droplet sizes match on a single map in terms of the impact parameter and of a new "symmetric" Weber number based on the sum of kinetic energies in the frame of the center of mass and on the sum of surface energies of the two droplets. Ashgriz and Poo ͓"Coalescence and separation in binary collisions of liquid drops," J. Fluid Mech. 221, 183 ͑1990͔͒ models are in agreement with our results, within experimental error. However, in this map, their representative curves depend on the diameter ratio. Simple formulas independent of the diameter ratio are therefore proposed to describe the transitions between regions representing outcomes of collisions.

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During a fire in an industrial facility, the main consequences concerning aerosol are the production of large amount of soot and potential resuspension of hazardous material in particulate form. Soot deposition quantification on walls in a room during a fire is essential for the prediction of aerosol quantities that can be transported in the ventilation ducts and clog high efficiency particulate air filters. For this purpose, accumulative resistive sensors, initially developed for monitoring Diesel Particulate Filters (DPF), have been used to quantify soot particles that are deposited on its sensing side. After validation of the fabrication process via electrical measurements, the sensor response has been studied under different polarization voltages and an experimental protocol for soot quantification has been qualified. Thanks to those protocols, it was first demonstrated that the polarization voltage has no influence on the deposition velocity. Then, the resistive sensor was calibrated at polarization voltages of 10 V and 0.1 V. For 0.1 V, results are less repeatable and do not allow to propose a correlation between conductance and deposited mass. Better repeatability was found for a polarization voltage of 10 V allowing to propose and develop a calibration procedure aiming to correlate sensor conductance and deposited mass of aerosol. Indeed, it was proved that the sensor has a blind zone, in terms of conductance, for mass deposit ranging from 0 to 230 mg/m 2 . A linear calibration curve with a good sensitivity of 2.49 µS.mg -1 .m 2 was obtained for deposited mass between 230 and 1630 mg/m 2 .