ATEX zones determine which equipment you may use where explosive atmospheres can occur. For gas, zones 0, 1 and 2 apply. For dust, zones 20, 21 and 22 apply. The zone determines the minimum equipment category.

Gas or dust?

Gas explosions are caused by flammable gases, vapours or mists. Dust explosions occur when combustible dust is suspended in the air in sufficient concentration. In powder handling, dust is the main concern, so the dust zones matter most.

The dust zones 20, 21 and 22

• Zone 20: an explosive dust cloud is present continuously, for long periods or frequently.
• Zone 21: an explosive dust cloud occasionally occurs during normal operation.
• Zone 22: an explosive dust cloud is not expected and only occurs briefly in case of a malfunction.

How is a zone determined?

The zone follows from the likelihood and duration of an explosive atmosphere. This assessment belongs in the explosion protection document. Determine zones per installation and per operating situation.

Which equipment belongs to which zone?

• Zone 20: at least category 1D (Da).
• Zone 21: at least category 2D (Db). Category 1D is also allowed.
• Zone 22: at least category 3D (Dc). Category 2D or 1D is also allowed.

Equipment with a higher category is always allowed. The category is shown on the nameplate. Check it before you order.

Why this matters for powders

Powders dust up during filling, transport and mixing. Fine fractions stay airborne longer. That is why the dust zone often determines the choice of motors, sensors, lighting and conveying equipment. Static electricity is an additional risk, so make sure the installation is properly earthed.

Frequently asked questions

What is the difference between zone 20 and zone 22?

In zone 20 the explosive dust cloud is present continuously or for long periods. In zone 22 it only occurs briefly in case of a malfunction.

Which category do I need for zone 21?

At least category 2D. Category 1D is also allowed.

Who determines the zone classification?

The owner of the installation, based on a risk assessment. We help with equipment selection and documentation.

Want to know which category you need for your installation? Contact us.