A hazardous explosive atmosphere can be devastating when the explosion occurs, leading to effects on people, the environment and property.
The prevention of the risk of these explosive atmospheres is based on specific regulations that must be applied in your company. We will first explain what constitutes an explosive atmosphere. How it is characterized and finally, how to control it and react in case of emergency.
What is a hazardous explosive atmosphere?
What is an explosive atmosphere?
An explosive atmosphere or (ATEX) is the mixture with air, under atmospheric conditions, of flammable substances in the form of gases, vapors or or dust in which, after ignition, combustion spreads to the entire unburned mixture.
When an explosive atmosphere is present (ATEX zoning) in a confined environment or a congested area, the effects in case of ignition will be serious or even catastrophic. Therefore, in these zones, the risks generated during maintenance work, new work or any other activity require prevention and protection measures that comply with regulations.
These rules take into account the choice of materials (protection index) to be installed in these areas, but also the prevention provisions, the availability to perform maintenance work.
How is an explosive atmosphere formed?
An explosive atmosphere is likely to form when a combustible material such as a gas, liquid or dust is mixed with air (or any other oxidizer) in sufficient concentration. This concentration must be between the lower explosive limit (LEL) and the upper explosive limit (UEL).
An explosion will occur as soon as the mixture is ignited.
The source of ignition or ignition must have sufficient energy called minimum ignition energy (MIE).
What are explosive atmosphere classification zones?
ATEX zones are classified according to the frequency and duration of the presence of an explosive atmosphere, as defined in the ATEX 1999/92/EC directive.
For explosive atmospheres due to the presence of gas, liquid or dust, the definitions are as follows:
- Zone 0 and 20: Location where an explosive atmosphere consisting of a mixture with air of flammable substances in the form of gas, liquid and dust is present in the air continuously or for long periods or frequently.
- Zone 1 and 21: Location where an explosive atmosphere consisting of a mixture with air of flammable substances in the form of gas, liquid and dust is likely to occur occasionally during normal operation.
- Zone 2 and 22: Location where an explosive atmosphere consisting of a mixture with air of flammable substances in the form of gas, liquid and dust is not likely to occur during normal operation or, if it does occur, is only of short duration.
In summary: Knowing the location and classification of the ATEX zones of your operation, training your personnel and respecting the regulations allows you to control this danger.
Risk assessment, the implementation of prevention and protection barriers, and compliance with the rules make it possible to maintain a high level of industrial safety compliance for production operations.