Hazardous Area Classification: Understanding Zones and Risks

Hazardous area classification is an essential process for identifying and delineating zones where there is the potential for explosive atmospheres to form, whether due to gases, vapors, or combustible dust. This process is crucial for safety in industrial installations, as it defines the areas that require specific protective measures to prevent explosions and fires.
The hazardous zones are categorized into different levels of risk, which vary according to the frequency and duration of the presence of explosive atmospheres:

• Zone 0 (Gas) / Zone 20 (Dust): Represents areas where explosive atmospheres are present continuously or for long periods. In these zones, maximum safety is required, as the possibility of explosion is constant.
• Zone 1 (Gas) / Zone 21 (Dust): Refers to areas where explosive atmospheres may occasionally form during normal operations. These zones require significant attention in terms of safety.
• Zone 2 (Gas) / Zone 22 (Dust): Indicates areas where explosive atmospheres are unlikely to occur, and if they do, it will be for short periods. It is the lowest risk zone within the hazardous areas, but still requires preventive measures.

The classifications for dust and gases are addressed separately due to their different physical characteristics, such as density, dispersion patterns, and ignition capability. Gases and vapors tend to disperse more rapidly, while dust can accumulate on surfaces and become dangerous when raised into the air.

Declassification of Hazardous Areas in a Grain Unloading Shed

In the context of industrial operations, reducing hazardous areas is an engineering strategy aimed at optimizing safety and operational efficiency. A practical example of this service can be observed in grain unloading sheds. In these facilities, trucks unload grain into hoppers, creating an environment prone to the formation of combustible dust, which can turn into explosive atmospheres.

In the previous situation, as shown in the first image, the entire interior area of the shed was classified as Zone 22 due to the risk of dust dispersion. Additionally, a critical Zone 21 area was identified within 4 meters around the hopper, where dust concentration is higher, and the risk of explosion is significant.

To mitigate these risks, our declassification proposal involved the enclosure of the truck unloading area within a specially designed chamber. This chamber is equipped with upper and side collectors that control dust dispersion and prevent it from spreading to other areas of the shed. The result of this intervention, as illustrated in the second image, was a significant reduction in hazardous areas. Zone 22 is now restricted to only 2 meters around the enclosure, while Zone 20 is confined within the chamber, where conditions are more controlled.

This solution not only reduced the risk of explosion but also increased operational efficiency, as the risk area was minimized, allowing for better circulation and use of space in the shed. Additionally, maintaining the hazardous areas became easier and less costly since the intervention zone was reduced and better controlled.

The use of this declassification technique demonstrates how engineering can be effectively applied to improve safety in industrial installations, complying with regulatory standards and optimizing operational processes.