Dust explosions and fires pose an industrial safety problem, due to the human and material losses caused by them. As many fuel processes and material transport generate powder particles, the effect of granulometry in different flammability properties has been studied to define the relationship between both. Deep knowledge of this relationship reduces the self-ignition and self-combustion processes, and the accidents associated with these processes. In this study, six different samples, including biomass, charcoal, and dog food, are tested in three different particle sizes, so differences in their flammability behavior could be appreciated (not only considering fine particles, but also coarse samples). The transport classification test was carried out, obtaining significant results in two samples, where the same material did not self-ignite when tested at its coarse size, but it did when tested at fine particle size. Similar results were obtained when analyzing initial temperature for related-combustion gasses emission: the finer the particle size, the lower the initial temperature. To understand the heat mechanisms, thermal analyses were performed, such as thermogravimetric analysis and differential scanning calorimetry. Finally, a self-ignition risk was assessed for all samples according to their activation energy and characteristic temperature. All the test results lead to conclude that biomasses easily start self-heating process, but its composition difficult the heat transmission to reach self-ignition, while charcoals are more susceptible to self-ignition.

In recent years, coal mine methane measurement techniques in mines have been gaining importance as poor firedamp control in work can cause the interruption of production and even fatal accidents. Since there is currently a variety of methane measurement equipment with different functional characteristics and measurement principles, a study is needed to indicate which type of equipment has the highest degree of confidence. This research presents the results of a study carried out by the Official Laboratory J. M. Madariaga (LOM) of the Polytechnic University of Madrid that aims to analyze the reliability of methane detection systems used in underground mining. Therefore, a series of portable and non-portable methane detectors with different measurement principles have been selected to subject them to laboratory tests following the methods described in the applicable regulations, such as time of response, dust effect, temperature, pressure, etc. The test equipment is usually the one used in the certification and calibration of these devices, subject to the LOM quality system. The results of these tests allowed for defining a marking system that led to a ranking of the tested methane detectors in order to find the advantages and disadvantages of each type. From the performed tests, a summary of the main sources of sensor inaccuracy was reported. It was found that catalytic sensors might present significant deviations when testing high concentrations in short periods of time or low concentrations during long periods of time. On the other hand, devices with an interferometric sensor can be unreliable as the measures are very sensitive to changes in environmental conditions, and optical sensors present longer response times than catalytic sensors.

The use of hydrogen as an energy vector seems today one of the most viable alternatives, although its use involves safety problems due to the generation of explosive atmospheres. Lower and upper flammability limits are one of the most important parameters at the time of characterize and handle flammable gases. This paper is focused on the evaluation of the safety prevention measures more commonly applied to explosive atmospheres, specifically the inertization, by means of a non-flammable gas (CO₂) in air-hydrogen mixtures. In this study both theoretical and experimental methods to determine the flammability interval have been carried out. The flammability limits and the LOC value are represented in a ternary diagram enable to determine the explosive area containing the entire range of explosive mixtures. The experimental study has been conducted in a flameproof chamber of 0.5 dm³ volume, designed to withstand explosions inside. The results show that the theoretical approaches are only valid as a previous step to the experimental tests, since the observed differences between both implies that the use of such approaches could lead to important safety risks.