In Europe, hazardous areas are classified into three zones which are directly related to the predicted occurrence of when and the duration that an explosive atmosphere may be present in the area. These zones are:

· Zone 0: Where an explosive atmosphere is continuously present, or present for long periods of time.

· Zone 1: Where an explosive atmosphere is likely to occur in normal operation.

· Zone 2:  Where an explosive atmosphere is not likely to occur in normal operation and if it does occur, it will exist only for a short time.   

Furthermore, European standards require that apparatus be subdivided into two groups: I and II. Group I is for apparatus to be used in mines where the danger is represented by methane gas and coal dust. Group II is for apparatus to be used in surface industries where the danger is represented by gas and vapor that has been subdivided into three groups:  A, B and C.

Hazard Type

The table above shows the similarities or differences between the North American and European practices regarding the classification of hazardous locations. It is important to note that in the table below, Zone 2 (IEC/Europe) and Division 2 (North America) are similar to a great extent but are not identical, while Division 1 includes the corresponding Zones 0 and 1. An instrument designed for Zone 1 cannot necessarily be directly used in Division 1, and no quantifications of the expressions “long period of time” for Zone 0, “can be present” for Zone 1 and Division 1, and “not normally present” for Zone 2, are given.

In common practice, for Zone 0, a level of probability of a dangerous mixture present more than 1% of the time is generally accepted. Locations classified as Zone 1 have a level of probability of a dangerous mixture between 0.01% and 1% (maximum 100 hours per year), while Zone 2 locations can be considered dangerous when said mixture is present for no more than one hour per year.

The main difference between the North American and the European classification of hazardous locations is that there is currently no direct equivalent to the European Zone 0 in the North American system; however, existing standards may be revised to allow an equivalent representation. Zone 0 is therefore the most dangerous. An instrument designed for Zone 0 must be incapable of generating or accumulating sufficient energy to ignite the fuel mixture.

Additional information Regarding ATEX

The primary intrinsically safe standard has been set in the European Union with the Directive 94/9/EC, commonly called ATEX (“Atmosphères Explosibles,” French for explosive atmospheres). The stated goal of the guidelines is to “help ensure the free movement of products in the European Union” by “minimizing the number of safeguard clause applications, at least those originating from divergent interpretations.” ATEX is intended to serve as total harmonization directive, laying down essential health and safety requirements, and

replacing existing divergent national and European legislation which covers the same subjects. The ATEX rules have been in place as a voluntary standard since March 1, 1996. The rules are mandatory on electrical and electronic equipment for use in environments subject

to explosion hazard sold in the EU as of July 1, 2003. IEC The International Electrotechnical Commission (IEC) is responsible for setting international standards for electrical technology. Its technical committee TC31 deals with explosion protection for electrical apparatus. It has introduced a procedure, the IECEx Scheme, which is intended to become a globally recognized test and certification procedure for explosion protection. The objective of the IECEx Scheme is to facilitate international trade in electrical equipment intended for use in explosive atmospheres by:

• reducing testing and certification costs to manufacturers

• reducing time to market

• providing international confidence in the product assessment process

• providing one international database listing The IECEx has not yet been ratified.

In The United States, Factory Mutual Research, managed by Factory Mutual (FM) Global, is a not-for-profit scientific and testing organization that has tested and certified over 40,000 products in the last 165 years. FM Research has set certification guidelines for equipment used in potentially explosive atmospheres. NEC The NFPA (National Fire Protection Association) 70, National Electrical Code, also known as the NEC, is the basis for all electrical codes in the United States. Classifications and related product markings for hazardous areas are covered in NEC 500 and 505. These are similar to, but not exactly the same as, those in ATEX. OSHA OSHA (Occupational Safety & Health Administration of the U.S. Department of Labor) participates in the US-EU Cooperation on Workplace Safety & Health. This is a project of the U.S. DOL, OSHA, and the EU European Agency for Health and Safety at Work. The goal is to promote sharing of information on current safety and health topics of common interest. Intrinsic safety is covered under Regulations (Standards - 29 CFR),   Hazardous (classified) locations 1910.307 and 1926.407. OSHA references the NEC guidelines for determining the type and design of equipment and installations which will meet this requirement. There are no global intrinsically safe standards or certifications.