Safety in Dust-Ex and Gas-Ex zones

Dust-Ex or Gas-Ex?

There is a risk of explosion if the following three conditions are all present at the same time:

1. Air
2. Flammable dust / flammable gas
3. Active ignition sources

Potentially explosive atmospheres are created by mixing air with flammable dusts (Dust-Ex) or flammable gases, vapours or mists (Gas-Ex). There must also be an active source of ignition which can ignite this flammable atmosphere.

Active sources of ignition include

Fire, flames, glowing embers	Electric sparks		Sparks caused by electrostatic discharge	Hot surfaces

PROTECTION: Safely prevent ONE of the three conditions

The choice is simple. Eliminate or prevent the development of potentially explosive atmospheres. This can be done, for example, by regularly cleaning away any dust deposits or by preventing their ignition. It is not always possible to prevent potentially explosive atmospheres. In these cases, precautions must be taken to prevent the ignition of these explosive mixtures. This is done by keeping equipment which is a possible ignition source away from the explosive atmosphere. It can also be done by designing equipment so that the likelihood of ignition is greatly reduced or eliminated altogether.
These are just some of the reasons for certifying and marking equipment used in potentially explosive atmospheres.

The basis for approving equipment for use in potentially explosive atmospheres is the Directive 94/9/EC (ATEX) valid in all EU member states since 30.06.2003
If an item of equipment is not Ex-protected, it cannot be used. Equipment for use
in potentially explosive atmosphere is classified into a series of categories depending on the potential hazard level involved.
ATEX defines categories and potential hazards as follows:

Definition of categories

Equipment approval groups

Classification of equipment for different zones