Large-scale usage of oxygen therapy (OT) may lead to increased oxygen concentrations (OC) in places where COVID-19 patients are treated. The aim of the study was to establish in an empirical way the OC in COVID-19 at the patient’s bedside and to assess the relationships and reactions that occur during OT in an uncontrolled oxygen-enriched environment. We analyzed and took into account the OC, the technical conditions of the buildings and the air exchange systems. Based on the results, we performed a Computational Fluid Dynamics analysis to assess evacuation conditions in the event of a fire outbreak in the COVID-19 zone. A total of 337 measurements of OC were carried out, and three safety thresholds were then defined and correlated with fire effects. The highest ascertained oxygen concentration was 25.2%. In the event of a fire outbreak at 25.2% oxygen in the atmosphere, the response time and evacuation of medical staff and patients is no longer than 2.5 min. Uncontrolled oxygen enrichment of the environment threatens the safety of medical staff and patients in COVID-19 hospitals.

On 2 October 2003 in Saint-Romain-en-Jarez (France) a fire in a farm building triggered an explosion in which 26 people were injured. Police investigation, based solely on an analysis of the effects and on general engineering knowledge, showed that the explosion was caused by an uncontrollably generated mixture of ammonium nitrate (AN) and molten plastic crates which formed an explosive mixture similar to ammonium nitrate fuel oil (ANFO). This is the only commonly known example of an ammonium nitrate blast taking place at its end user destination. Is such an explanation of the incident plausible and could a similar blast possibly happen anywhere else? The experimental results support this thesis of French investigators but raise further doubts. Laboratory reconstruction of the self-acting process of generating the explosive material confirmed the investigators’ report. However, other materials at the incident site could have influenced the final outcome too. The lab-recreated explosion of a mixture of AN and molten plastic partially confirmed the report’s thesis.

The main purpose of this study was to analyze the impact of some parameters (water mist flow rate and type of gas used) of the hybrid extinguishing system on the fire environment (temperature as well as carbon monoxide and oxygen concentrations) in a closed room. Hybrid fire-extinguishing systems in which water mist is driven by inert gas combine the advantages of typical fog systems and fixed gas extinguishing devices. They have been developed in the last years but are now being used more and more often and the preparation of standards for them is planned for 2020. For this purpose, many fire tests with this system should be conducted. Some of them are discussed in this paper. Two different flow rates of water mist (1.5 or 3 dm³/min) and inert gas (nitrogen or air) were used during hybrid system testing. Some parameters of the fire environment in the compartment such as temperature measured by thermocouples as well as carbon monoxide and oxygen concentrations measured by electrochemical gas sensors are presented here. The characteristic values of the extinguishing process are also included. The assumed times of ensuring safe conditions in the room have been confirmed.

Ammonium nitrate (AN) is a strong oxidizer that undergoes phase transitions and thermal decomposition at relatively low temperatures. This—as verified by historical facts—constitutes a challenge for the fire department during rescue operations. AN is also a highly reactive material widely used for the production of, i.a., fertilizers and explosives. The latter are popular not only in military applications but also in industrial ones, such as mining. They include ammonites and amatols utilized in coal mining, as well as Ammonium Nitrate Fuel Oil (ANFO) utilized in, i.a., rock mining. As a simple and cheap material, ANFO also tends to be used by terrorists. The spontaneous formation of an AN and polymers mixture—similar to ANFO in terms of composition and explosion force—was observed in fire conditions during previous research. At individual stages (from creation to exploitation), AN often comes into direct contact with various polymers. Polyolefins, in particular polyethylene (PE) and polypropylene (PP), are among the most popular groups of such materials. They are used for the production of, i.a., foil packaging and flexible intermediate bulk containers for the storage and transport of fertilizers. Despite the frequent mutual contact of these materials, there is little information in the literature on the interaction of AN and its polymer-made packaging in fire conditions. For this reason, it was decided to conduct a series of thermal analyses using Differential Scanning Calorimetry (DSC) to study the material behavior under the influence of high temperature. As it turns out in practice, the spontaneous formation of a mixture similar to ANFO—in terms of composition and explosion force—can be observed in fire conditions. Due to the results indicating a potentially explosive course of the reaction, laboratory tests on the macro scale were also carried out. The performed observations show that it may be necessary to create a procedure containing several different test methods in order to predict a mixture’s behavior during a fire and to define the appropriate guidelines for firefighting teams. Such guidelines would enable firefighters to prepare the right equipment during a firefighting operation and to develop a strategy based on the observed course of events.

This article is a continuation of a case study in which we presented the results of research on processes generated under fire conditions by mixing molten ammonium nitrate (AN) with selected polymers. Here, we present an analysis of how certain materials, which may frequently appear in farm buildings and are commonly used in the immediate vicinity of humans, can potentially form explosives. The chosen materials include polyamides (PA) from which the wear-resistant machine elements are made (e.g., high-performance gears, wheels of transport trolleys); polyvinyl chloride (PVC) used, i.e., in construction carpentry, electrical insulation, and hydraulic pipes; polystyrene (PS) used, i.e., in insulation and containers; and poly(methyl methacrylate) (PMMA), i.e., so-called organic glass and plexiglass. The research results showed that these seemingly harmless and safe materials, mixed with AN and heated under fire conditions, may turn into explosives and stimulate stored AN. This creates significant risks of an uncontrolled fire progress.

The advantage of hybrid fire suppression systems is that they combine the advantages of both water mist and clean agent systems. Currently, this innovative technology is increasingly used in fixed firefighting systems. Available literature both in Polish and around the world describes this issue in a fragmentary way. Extinguishing system tests were carried out at the Main School of Fire Service in Warsaw. The impact of water mist flow rate on the temperature variability in a closed room during the extinguishing of group A fires using a hybrid water mist system was analyzed. Four different flow rates 0.5, 1.0, 1.5 and 3.0 dm³/min were applied. The temperature variability of selected points of a closed test chamber during extinguishing process are presented. The extinguishing efficiency, taking into account extinguishing time, average speed of temperature drop and other parameters, was estimated on the basis of proposed original criterion. The results obtained showed that water flow rate has a significant impact on temperature variability and included the determination of optimal water flow rate at which the extinguishing efficiency is the highest. The conducted research proved that the hybrid system is more effective than classic mist and gas systems when extinguishing group A fires.