Since 1996 in Europe it has been mandatory for machinery manufacturers and users to produce and to buy machinery in compliance with the Machinery Directive 89/398 

The ATEX European Directive is for machinery components and controls that work in Explosive Atmospheres.

ATEX stands for ATmosphere EXplosive and requires the employer and / or user to prevent and provide protection against explosions.

With regard to explosion protection in a potentially explosive atmosphere, the ATEX directive 94/9/EC takes precedence over the Machinery Directive and has to be applied.

The Equipment Directive 94/9/EC (ATEX) has been implemented into United Kingdom law by Statutory Instrument (S.I.) 1996:192  

Where workplaces, which contain areas where explosive atmospheres may occur, are already in use before 30 June 2003, ATEX states that they shall comply with the minimum requirements set out in the ATEX Directive no later than July 2006.

Additionally, if, after 30 June 2003, any substantial modification, extension or restructuring is undertaken, then the user shall take the necessary steps to ensure that the final configuration complies with the Directive.

The Directive says that you must :

• Characterise how often a potentially explosive atmosphere will be present and where.
• These areas are then zoned according to the specifications here.
• Then ensure only equipment of the correct category is in a particular zone type. Once an area has been identified as being dangerous, this then determines the restrictions needed on potential sources of ignition that may be present in that area.