Ventilation Requirements in an ATEX Atmosphere

What is an explosive atmosphere? An explosive atmosphere (ATEX) is one in which the air contains flammable elements and, therefore, there is a risk of explosion. Of course, this type of atmosphere should always be avoided in the workplace. However, in some cases, the presence of flammable gases, vapors, or dust is inevitable, either due to the activity itself or due to collateral effects of the activity. An example of the latter is the case of flammable substances that, inadvertently, appear when storing alkaline solutions or weak acids in metal containers and, due to an electrochemical reaction, hydrogen is formed and accumulates in the gaseous phase.

It is important to note that we talk about ATEX atmosphere when normal atmospheric conditions exist without the presence of pyrotechnic or explosive materials and, when an ignition occurs, the combustion spreads to the unburned elements.

ATEX Atmospheres: Protection Measures

If there is a risk of forming an ATEX atmosphere, protective measures must be taken. First, efforts should be made to prevent such atmospheres. If it is not possible to avoid their appearance, measures must be taken to prevent ignition sources. When this is also not possible, mitigation measures must be taken.

Ventilation as Prevention

When it is impossible to prevent the escape of flammable substances, proper ventilation can help prevent the formation of ATEX atmospheres. How to assess the effectiveness of such ventilation? The following parameters should be considered:

• For gases, vapors, and mists, the sizing of the ventilation system must take into account the flow of substances that may escape, know the location of the source, and the conditions of its diffusion.

• For dust, preventive actions include suction at the source and the prevention of hazardous dust accumulation.

• While proper ventilation cannot prevent the occurrence of ATEX atmospheres in 100% of cases, it can minimize the possibility of their formation.

Requirements for Ventilation Systems in ATEX Atmospheres

Currently, there are two types of directives: ATEX 95 directive 94/9/EC, which regulates equipment and protection systems, and ATEX 137 directive 99/92/EC, which establishes minimum requirements to improve safety in workplaces where these explosive atmospheres occur.

Since ventilation systems that incorporate ATEX atmospheres are electrical equipment, they must also comply with current regulations. Thus, ventilation equipment must be located inside an explosion-proof enclosure, so that in the event of a combustion, the enclosure can withstand the explosion and prevent leaks through its joints. In addition, this hermetic enclosure must prevent the entry of flammable gases or vapors.

Before carrying out any activity in a workplace where an explosive atmosphere exists, the entire enclosure must be inspected as a whole. Thus, the ventilation system and all other installations must be reviewed. The protective measures adopted must be periodically inspected by trained personnel with extensive knowledge in the field. In the case that ventilation systems have mechanisms, an inspection must be carried out each time a new adjustment is made. It is also advisable to use locking mechanisms for such installations to avoid unintentional adjustments.