Spontaneous combustion is a phenomenon that results from the heating of combustible organic powders by slow oxidation and which occurs through the air passage (created by an air depression) through the mass of dust. The oxidation phenomenon of combustible powders represents their reaction with atmospheric oxygen resulting in products of carbon dioxide, carbon oxide, water and other gases whose content depends on the temperature at which the oxidation takes place. The self-ignition of combustible dusts depends on their chemical composition, the properties of component substances, on the particle size and geometry of the material mass and, last but not least, on the temperature of the environment. Due to global worries of sustainability in construction engineering the trend is to use ecofriendly organic waste to various purposes as in construction materials. The challenge is that by using this kind of materials one should ensure the safety related to the process of such organic materials which are known to have combustible properties. The purpose of this work is to present the self-ignition behavior of combustible dusts such as sunflower and wood by means of drying tests under constant temperature conditions.

The aim of this paper was to determine the concentration of heavy metals in dust samples by the method of analysis by inductively coupled plasma optical emission spectrometry (ICP-OES) and to assess the degree of pollution of the studied areas. The dust samples studied and subjected to analytical analyzes were collected from the vicinity of industrial areas and urban areas of localities in the Jiu Valley, a monoindustrial area. The main heavy metals determined were: Cu, Zn, Pb, Ni, Cr, Co etc. Dust particles depending on their origin can be inorganic or organic. The samples were collected from the urban areas and from the vicinity of the industrial areas.

Agricultural waste is found in abundance in the environment, whether it is the plant itself represented by the stem, leaf or seeds that have been peeled or other waste. By drying and crushing the residues from the plants, organic powders will be formed with a variable granulation and humidity. Through the processing of oilseeds such as sunflower seeds, significant amounts of waste from seeds result. Seed shells resulting from technological processes crumble, forming fine powders, whose granulations are different. A certain percentage will be 63μm or smaller and if those fine powders are mixed with air can form clouds with explosive properties. The purpose of this paper was to determine the minimum ignition layer and cloud temperatures. Experimental determination of flammability parameters is particularly important in order to take the proper safety measures so that accidents can be avoided.