What are Class 1 / Division 2 and ATEX Zone 2 certifications?

Explosions can cause significant damage, along with severe injury or worse loss of life. To prevent explosions from happening in harsh environments whereby flammable gases or combustible dust is present directives and guidelines are put in place to protect the public, workforce, and environment.

Both the USA and the European Union have their certifications and guidelines to control the risks of dangerous substances igniting.

The below defines explosive atmospheres, summarises the regulations in both the USA and the European Union and demonstrates Industrial Computers, Panel PCs and Data Acquisition hardware certified for installation in explosive atmospheres.

According to The Dangerous Substances and Explosive Regulations, commonly known as DSEAR, an explosive atmosphere is defined as a mixture of dangerous substances within the air under atmospheric conditions.

The atmospheric conditions are most commonly referred to by their ambient temperatures and pressures, for example, a temperature of –20°C to 40°C and a pressure of 0.8 to 1.1 bar. Three components are necessary for an explosion to occur:

An explosive atmosphere may be found in public spaces and within the workplace across many different industries. An example of an explosive atmosphere whereby flammable gases or vapours are present would be a fuelling station. An explosive atmosphere whereby organic dust such as grain flour or wood is present would be a timber sawmill.

Protecting the public, workforce and environment from explosive atmospheres is paramount but not a universal standard. Both the USA and the European Union have similar standards but are defined slightly different to each other.

In the US, NEC (National Electric Code) is adhered to, which puts HAZLOC (Hazardous Locations) into classes, divisions (and groups for the type of materials present) and for Europe, the IEC (International Electrotechnical Commission) classifies HAZLOC by zones. Products such as a panel PC will then be certified to be safe in these areas before they can be applied.

In North America, products are listed by the UL (Underwriters Laboratories, a global safety consulting and certification company based in the US and 45 other countries), which determines the level of Class and Division certification the product is suitable for.  ATEX uses certified bodies to classify products for use in the EU.

Outside the European Union, regulations apply under the IEC Ex (International Electrotechnical Commission – System for Certification to Standards Relating to Equipment for Use in Explosive Atmospheres).

The IEC Ex is a voluntary system which provides an internationally accepted means of proving compliance with IEC standards.

IEC standards are used in many national approval schemes and as such, IEC Ex certification can be used to support national compliance, negating the need in most cases for additional testing.

Divisions go further in classifying how often the flammable or explosive substances are likely to be present under normal operating conditions.

Division 1            Flammable substances are continually present or are likely to exist under normal operating conditions.

Division 2            Flammable substances are not likely to exist under normal operating conditions.

The abbreviation ATEX is derived from the French words, ATmosphères EXplosibles and represents 2 European directives stipulated for controlling explosive atmospheres:

1) Directive 99/92/EC (also known as ‘ATEX 137’ or the ‘ATEX Workplace Directive’) on minimum requirements for improving the health and safety protection of workers potentially at risk from explosive atmospheres.

2) Directive 94/9/EC (also known as ‘ATEX 95’ or ‘the ATEX Equipment Directive’) on the approximation of the laws of Members States concerning equipment and protective systems intended for use in potentially explosive atmospheres.

ATEX classifications are in zones, derived from the US ‘HAZLOC’ standard. They combine the ‘Class’ area classification and the ‘Division’ likelihood of explosive substance presence.  It subdivides powders and dust from gases and vapours.

ATEX Zone 0

A place in which an explosive atmosphere consisting of a mixture with air of dangerous substances in the form of gas, vapor or mist is present continuously or for long periods or frequently.

ATEX Zone 1

A place in which an explosive atmosphere consisting of a mixture with air of dangerous substances in the form of gas, vapor or mist is likely to occur in normal operation occasionally.

ATEX Zone 2

A place in which an explosive atmosphere consisting of a mixture with air of dangerous substances in the form of gas, vapor or mist is not likely to occur in normal operation but, if it does occur, will persist for a short period only.

Class 1 / Division 1 – Zone 0 & Zone 1

Where ignitable concentrations of flammable gases, vapours, or liquids:

Class 1 / Division 2 – Zone 2

Where ignitable concentrations of flammable gases, vapours, or liquids:

Are not likely to exist under normal operating conditions.

Are normally in closed containers where the hazard can only escape through accidental rupture or breakdown of such containers or in case of abnormal operation of equipment.

Where embedded electrical products are concerned, the requirement for harsh environment industries such as oil and gas will usually be certification to Class 1 / Division 2 and/or ATEX Zone 2.