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General Points

This Directive entitled Minimum requirements for improving the safety and health protection of workers potentially at risk from explosive atmospheres imposes requirements on site operators and employers. In general terms, in the UK, it covers ground already dealt with by the Health and Safety at Work etc. Act but there are some specific points which will need addressing by site operators and employers although for well organised and managed sites the majority of the work required will simply be a case of bringing together existing documents and procedures. (See Main requirements below)  The Directive requires that measures are taken to to ensure that work in explosive atmospheres can be carried out safely (see Article 5 of the Directive), and these measures must be co-ordinated with other employers (if there are several employers serving the same site).  (See Article 6 of the Directive)

Its implementation in the UK is the responsibility of the Health and Safety Executive (HSE) and the applicable regulations are known as the Dangerous Substances and Explosive Atmosphere Regulations (DSEAR) which also covers the requirements of the safety aspects of the Chemical Agents Directive (Directive 98/24/EC).

DSEAR came into force on 9 December 2002 as Statutory Instrument 2002/2776.  The regulations can be downloaded from the HSE web site. (Use the Useful Links page) The HSE also publish an Approved Code of Practice and Guidance to DSEAR.  (May be obtained from HSE Books - See Useful Links Page)

 

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Main Requirements of the Directive

Prevention and Protection - Principles

Employers (those with places of work which have hazardous areas) are required to prevent and provide protection against explosions. (see Article 3 of the Directive)

 
The basic principles set out in the Directive for explosion prevention and protection are (in order of priority):

>

the prevention of the formation of explosive atmospheres, or where the nature of the activity does not allow that...
> the avoidance of the ignition of the explosive atmospheres, and ...
> the mitigation of the detrimental effects of an explosion so as to ensure the health and safety of workers.

The measures shown above shall be reviewed regularly and always when significant changes occur.

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Assessment of Explosion Risks

An assessment of explosion risks must be carried out. (See Article 4 of the Directive) ...

The assessment shall at least take account of ....
> 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 risks shall be assessed overall. Places which are or can be connected via openings to places in which explosive atmospheres may occur shall be taken into account in assessing explosion risks.

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Requirements Where an Explosive Atmosphere May Occur

(See Article 7 of the Directive)

(It should be appreciated that the evaluation required by the Directive (and by DSEAR) may not necessarily result in there being a hazardous area.  Only where the assessment shows that there is a hazardous area do the following requirements apply.)

 

> the employer shall classify places where explosive atmospheres may occur into zones (Annex I of Directive)
> the employer shall ensure that the minimum requirements (laid out in Annex II of the Directive) are applied to places classified into zones (See below)
> before first use, the workplace shall be verified as complying with the Directive by a competent person
> Hazardous Area Marking  Where necessary, places where explosive atmospheres may occur in such quantities as to endanger the health and safety of workers shall be marked with signs at their point of entry. [The hazardous areas marking: the letters 'EX' in black within a black outlined triangle with yellow background. (As shown at the top of this page.)]

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Explosion Protection Document

An explosion protection document must be drawn up (See Article 8 of the Directive) and kept up to date.

 

 

The explosion protection document shall demonstrate in particular ...
> that the explosion risks have been determined and assessed
> that adequate measures will be taken to attain the aims of the Directive
> those places which have been classified into zones
> those places where the minimum requirements (set out in Annex II of the Directive) will apply
> that the workplace and work equipment, including warning devices, are designed, operated and maintained with due regard for safety
> that [in accordance with Directive 89/655/EEC] arrangements have been made for the safe use of work equipment

The explosion protection document shall be drawn up prior to commencement of work and be revised when the workplace, work equipment or organisation of the work undergoes significant changes, extensions or conversions.  Existing explosion risk assessments, documents or reports may be combined to form the explosion protection document.

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Minimum Requirements  for Improving the Safety and Health Protection of Workers Potentially At Risk From Explosive Atmospheres (Annex II of the Directive)

 

The following are identified as being key to the safety in classified hazardous areas or to equipment located in non-hazardous areas which impinges on the safety of hazardous areas
> The employer must provide those working in places where explosive atmospheres may occur with sufficient and appropriate training with regard to explosion protection.
> Where required by the explosion protection document:
- work in hazardous places must be carried out in accordance with written instructions issued by the employer,
- a system of permits to work must be applied for carrying out both hazardous activities and activities which may interact with other work to cause hazards.
Permits to work must be issued by a person with responsibility for this function prior to the commencement of work.
> Any escape and/or release, whether or not intentional, of flammable gases, vapours, mists or combustible dusts which may give rise to explosion hazards must be suitably diverted or removed to a safe place or, if that is not practicable, safely contained or rendered safe by some other suitable method.
> If an explosive atmosphere contains several types of flammable and/or combustible gases, vapours, mists or dusts, protective measures shall be appropriate to the greatest potential risk.
> Prevention of ignition hazards in accordance with Article 3 must also take account of electrostatic discharges, where workers or the working environment act as charge carrier or charge producer. Workers must be provided with appropriate working clothes consisting of materials which do not give rise to electrostatic discharges that can ignite explosive atmospheres.
> Plant, equipment, protective systems and any associated connecting devices must only be brought into service if the explosion protection document indicates that they can be safely used in an explosive atmosphere. This applies also to work equipment and associated connecting devices which are not regarded as equipment or protective systems within the meaning of Directive 94/9/EC if their incorporation into an installation can in itself give rise to an ignition hazard. Necessary measures must be taken to prevent confusion between connecting devices.
> All necessary measures must be taken to ensure that the workplace, work equipment and any associated connecting device made available to workers have been designed, constructed, assembled and installed, and are maintained and operated, in such a way as to minimise the risks of an explosion and, if an explosion does occur, to control or minimise its propagation within that workplace and/or work equipment. For such workplaces appropriate measures must be taken to minimise the risks to workers from the physical effects of an explosion.
> Where necessary, workers must be given optical and/or acoustic warnings and withdrawn before the explosion conditions are reached.
> Where required by the explosion protection document, escape facilities must be provided and maintained to ensure that, in the event of danger, workers can leave endangered places promptly and safely.
> Before a workplace containing places where explosive atmospheres may occur is used for the first time, its overall explosion safety must be verified. Any conditions necessary for ensuring explosion protection must be maintained.
Such verification must be carried out by persons competent in the field of explosion protection as a result of their experience and/or professional training.
> Where the risk assessment shows it is necessary:
- it must be possible, where power failure can give rise to the spread of additional risks, to maintain equipment and protective systems in a safe state of operation independently of the rest of the installation in the event of power failure,
- manual override must be possible in order to shut down the equipment and protective systems incorporated within automatic processes which deviate from the intended operating conditions, provided that this does not compromise safety. Only workers competent to do so may take such action,
- on operation of the emergency shutdown, accumulated energy must be dissipated as quickly and as safely as possible or isolated so that it no longer constitutes a hazard.
> If the explosion protection document based on a risk assessment does not state otherwise, equipment and protective systems for all places in which explosive atmospheres may occur must be selected on the basis of the categories set out in Directive 94/9/EC.

 

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