Hazardous areas

EXPLOSION

An explosion is a release of energy (mechanical, chemical…) in a sudden and often violent manner with high temperature and high pressure due to oxidation or another exothermic reaction.

EXPLOSIVE ATMOSPHERE

An explosive atmosphere is a result of the mixture with air, under atmospheric conditions, and flammable substances in the form of gas, vapor, dust, fibers or flyings which, after ignition, permits self-sustaining propagation.

A POTENTIALLY EXPLOSIVE ATMOSPHERE

An atmosphere is defined as potentially explosive when its usual composition is not explosive, but due to unforeseen circumstances, it can vary to such an extent that it becomes explosive (the danger exists as a potential state).
 
Main foreseeable circumstances are as follow:
• various stages of a manufacturing process,
• incidents or accidents (rupture of a pipe-line, leak, supply loss),
• meteorological conditions (high ambient temperature, air movements).

CONDITIONS FOR EXPLOSION

AREAS CLASSIFICATION DEFINED BY DIRECTIVE 1999/92/EC

ATEX / IECEX CLASSIFICATION

GAS AND VAPORS EXPLOSION

In general, the substances, gases, liquids or vapors which can be at the origin of explosion are:
• heating gas,
• hydrocarbons,
• glue and adhesive solvents,
• varnishes and resins,
• manufacturing additives for pharmaceutical products, artificial dyes, aromas and perfumes,
• manufacturing agents for the following materials : plastics, rubbers, man-made textiles and chemical cleaning products,
• products used in the treatment and manufacturing of alcohols and derivatives…
 

DUST EXPLOSION


Organic and metallic products which create powder and dust form can also in certain conditions become active agents of an explosion.
These are powders and dust of:
• magnesium,
• aluminum,
• sulfur,
• cellulose,
• corn starch,
• epoxy resins,
• polystyrenes,
• dust of plastic,
• coal,
• wood,
• medics,
• sugar (icing sugar),
• flour...
 

GAS AND VAPORS CLASSIFICATION AND TEMPERATURE CLASSIFICATION


Gases are divided into
• three groups bi IEC / EN
• four groups by the CEC (Canadian Electrical Code) and the NEC (National Electrical Code - US).
The IEC also defines different groups of gases and vapors.
The IEC and North American groups are viewed as fundamentally the same, see following table.

DUST CLASSIFICATION

IEC / EN defined a classification of dust:

EXAMPLES OF FLAMMABLE SUBSTANCES