A quick guide to the ATEX 137 Workplace Directive

Definition

The directive defines an explosive atmosphere as a mixture of air and flammable gasses, vapors, mists, or dusts, where ignition would lead to the combustion of the entire flammable substance.

However, as it’s covered by other regulations, the directive does not apply to:

• Areas used directly for medical treatment of patients
• Use of appliances burning gaseous fuels
• The manufacture, handling, use, storage, and transport of explosives or
• Chemically unstable substances
• Mineral-extracting industries 
• Transport by land, water, and air, except means of transport intended for use in a potentially explosive atmosphere

Assessment of explosion risk

The employer must assess the specific risks of the explosive atmospheres and places that are or can be connected via openings to the explosive atmospheres. The risk assessment should consider:

• The likelihood that explosive atmospheres will occur and their persistence
• The likelihood that ignition sources, including electrostatic discharges, will be present and become active and effective
• The installations, substances used, processes, and their possible interactions
• The scale of the anticipated effects

Explosion protection document

Before any work can commence, the employer must write an explosion protection document that must demonstrate:

• That the explosion risks have been determined and assessed
• That adequate measures will be taken to comply with the directive
• The places where the minimum requirements (described below) apply
• That the workplace and work equipment, including warning devices, are designed, operated, and maintained with due regard for safety

The document must be revised when the workplace, work equipment, or organization of the work undergoes significant changes, extensions, or conversions.

Classification of zones

Hazardous places are classified into zones based on the frequency and duration of the occurrence of an explosive atmosphere. Of six zones, three are for flammable substances in the form of gas, vapor, or mist (Zone 0, 1, and 2), while three are for combustible dust (Zone 20, 21, and 22):

• Zones 0 and 20 are for places where an explosive atmosphere is present continuously, or for long periods or frequently.
• Zones 1 and 21 are for places where an explosive atmosphere is likely to occur occasionally.
• Zones 2 and 22 are places where an explosive atmosphere is not likely to occur, and if it does, it will only be for a short period.

These zones decide what equipment and protective systems to be used, based on categories set out in the . ATEX 114 equipment directive (2014/34/EU).

Minimum requirements

The directive describes the minimum requirements to improve the protection of the worker’s safety and health in potentially explosive atmospheres.

This includes some general requirements, such as training of the workers, written instructions, and work permits for hazardous activities, in addition to certain explosion protection measures:

• Any escape or release of flammable substances must be diverted, removed, contained, or rendered safe by another method.
• Ignition prevention must also cover electrostatic discharge. Workers must be provided with appropriate work clothes in materials that don’t cause electrostatic discharges
• The workplace, work equipment, and any associated connecting device must be designed, constructed, assembled, installed, maintained, and operated to minimize the risk of explosion.
• Where necessary, workers must be given a warning by lights or sound to have time to evacuate before the explosion conditions are reached.
• Where necessary, escape facilities must be provided and maintained to ensure that workers can leave endangered places promptly and safely in the event of danger.
• Before using a workplace where explosive atmospheres may occur for the first time, a competent person must verify its overall explosion safety. Any conditions necessary for ensuring explosion protection must be maintained.
• If a power failure can increase the risk, it must be possible to maintain equipment and protective systems independent of the rest of the installation.
• Equipment and protective systems incorporated with automatic processes must be possible to shut down with a manual override.

Classification of zones

Hazardous places are classified into zones based on the frequency and duration of the occurrence of an explosive atmosphere. Of six zones, three are for flammable substances in the form of gas, vapor, or mist (Zone 0, 1, and 2), while three are for combustible dust (Zone 20, 21, and 22):

• Zones 0 and 20 are for places where an explosive atmosphere is present continuously, or for long periods or frequently.
• Zones 1 and 21 are for places where an explosive atmosphere is likely to occur occasionally.
• Zones 2 and 22 are places where an explosive atmosphere is not likely to occur, and if it does, it will only be for a short period.

These zones decide what equipment and protective systems to be used, based on categories set out in the . ATEX 114 equipment directive (2014/34/EU).