Explosion-proof equipment must be designed so that the ignition of the surrounding explosive atmosphere to be avoided. This is very important because an explosion can have particular implications over goods, life and not least over the environment. One of the ignition sources of an explosive atmosphere is represented by hot surfaces. Each equipment designed to operate in explosive atmospheres develops a maximum surface temperature. The specific standards used to assess explosion protection characteristics cover only indirectly and in part the factors influencing the maximum surface temperature. By this study, using a standardized testing methodology, the factors influencing the maximum surface temperature in case of explosion-proof luminaires with type of protection flameproof enclosure "d" and increased safety "e" were pointed out and analyzed (i.e. maximum designed ambient temperature of the luminaire; placement of temperature sensors to capture the points where the maximum surface temperature is recorded; type, power and size of the light source installed in the luminaire; operating position of the luminaire; supply voltage of the luminaire). The measures to be taken, in order to determine as accurately as possible the maximum surface temperature, in relation with the influencing factors, were also identified.

Current legislation regulates the obligations and responsibilities of persons who perform design, manufacture and use of equipment and installations in potentially explosive atmospheres with regard to compliance with explosion prevention requirements. There are two European Directives, so-called ATEx Directives, which regulate the placing on the European market of products intended for use in potentially explosive atmospheres and their safe use: Directive 2014/34/EU and Directive 1999/92/EC. The paper presents some aspects regarding the border situations where the two directives apply, in the case of assemblies of equipment to be assessed by a manufacturer in accordance with the Directive 2014/34/EU for putting on the market and the installations that are equipment assembled by the user under his responsibility and have to be assessed by users toward with the Directive 1999/92/EC requirements.

The research carried out in the specialized Laboratory of the National Institute for Research and Development in Mine Safety and Explosion Protection-INSEMEX Petrosani has identified the causes of high pressure peaks occurrence in the case of large electric motor enclosures as: the extremely large internal volume, the geometrical shape of motor enclosures and the very intricate and complex internal arrangement of such motor enclosures, having in mind the tendency of motor manufacturers for chemical and petrochemical industry to manufacture motors having more complex geometrical shapes. These results proved to be very useful in assisting designers of large flameproof electric motors to improve motors design so as to make them more reliable when testing in explosive mixtures.

The risk of explosion becomes significant when, in the industrial field, flammable substances such as gases, vapours, mists, dusts, lint and fibres may be present. If they are present in sufficient quantity, the risk of explosion is imminent. On the other hand, the measure of shutting down the technical equipment, in the context of the presence of explosive atmospheres, is not an acceptable measure in all situations. As examples are the parts of installations that have safety functions: ventilation installations, installations for monitoring the concentration of flammable substances and other safety parameters. Explosion protection of technical equipment shall be evaluated and tested in order to validate it. The testing process of the technical equipment for the purpose of explosion protection certification is situated at the confluence of several engineering fields: mechanical, electrical, chemical, etc. The first part of the paper deals with the risk of explosion and presents the explosion protection of the technical equipment. The systematized presentation of the technical equipment tests is performed in the second part of the paper. Among the conclusions it is mentioned that although the field of tests in explosion atmospheres is an interdisciplinary one, its coherence is ensured by the specific standards.

Abstract. Explosive risk occurs in all activities involving flammable substances in the form of gases, vapors, mists or dusts which, in mixture with air, can generate an explosive atmosphere. As explosions can cause human losses and huge material damage, the assessment of the explosion risk and the establishment of appropriate measures to reduce it to acceptable levels according to the standards and standards in force is of particular importance for the safety and health of people and goods