Spaces where substances that may form explosive mixtures with air (or other oxidants) are used, produced or processed are considered to be at risk of explosion. The assessment of the explosion hazard of rooms and external spaces includes identifying them and designating appropriate explosion hazard zones within them.

An explosion is a phenomenon caused by the release of large amounts of energy, accompanied by a sudden increase in temperature and pressure, emission of radiation (flash) and the generation of an acoustic wave. A chemical explosion is caused by a violent, exothermic reaction, e.g. combustion.

An explosion may occur when an explosive mixture is created, such as a mixture of flammable gas and air in appropriate proportions of both components. The category of explosive mixtures also includes air-dust mixtures. Some dusts from non-flammable materials are combustible (such as aluminum dust or tin dust) and may form explosive mixtures. A potential explosion hazard exists when such dust clouds are ignited by a blast of air and contain very small grains or fibers.

Various entities are responsible for assessing the explosion risk in a given zone, including the investor, the entity designing the building and the user, who makes decisions regarding the devices used and the technological process. When making this assessment, all factors and circumstances that may affect the formation of an explosive mixture are taken into account. This includes the type of potential hazard source, flammable ingredients, ventilation system, release time, pressure, temperature and many other factors. In the case of liquids, the flash point and operating temperature play an important role – an explosive mixture may be formed when the liquid temperature reaches the flash point.

The following classification of rooms and external spaces at risk of explosion applies:

• ZO zone – an explosive mixture of gases and vapors of flammable liquids occurs constantly or for a long time, e.g. in tanks above the liquid surface in depressions, unventilated channels, etc.;
• zone Z1 – an explosive mixture of gases and vapors of flammable liquids occurs temporarily during normal operation, e.g. around ventilation chimneys, when filling tanks, when using flammable liquids for painting, washing, cleaning, dyeing, gluing, diluting, etc.;
• zone Z2 – an explosive mixture of gases and vapors of flammable liquids occurs rarely, for a short time and in a small volume, e.g. around seals of pumps, valves, leaks in technological installations, etc.;
• zone Z10 – an explosive mixture of dust or flammable fibers with air occurs in the form of a cloud, e.g. during the processing of certain conductive materials and during pouring, grinding, grinding, cleaning and vibration, or inside technological equipment;
• zone Z11 – an explosive mixture of dust or fibers with air may occur in a short time as a result of draft, oxidation, wind and other forces causing dust to be lifted.

Open flames must not be used in objects at risk of explosion. Lightning protection in a reinforced version is required.

Only necessary electrical equipment is used in areas exposed to the risk of explosion. These devices must be so constructed as to preclude the possibility of a spark or excessive heating which could ignite a possible explosive mixture. Devices of this type, which have been designed with measures to prevent or impede the ignition of explosive mixtures outdoors, are referred to as explosion-proof electrical devices. Their design must ensure that the temperature of the external surfaces of these devices is lower than the temperature of the explosive mixture in the environment, both during normal operation and in the event of disturbances. In addition,

Source:https://www.seka.pl/strefa-zagrozenie-wybuchem/

Supported by Norway through Norway Grants 2014-2021, in the frame of the Programme “Social Dialogue – Decent Work”.