Explosion Risk Assessment (ERA)

An Explosion Risk Assessment should provide a comprehensive assessment of hazards associated with the possibility of an explosion. It should take into account, among other things, the likelihood and duration of the occurrence of an explosive atmosphere, the likelihood that ignition sources may occur and become active — including electrostatic discharges — as well as the substances and mixtures used, installations, process conditions, interactions between processes, and the possible consequences of an explosion.

In this preliminary audit, ERA refers to the documented explosion risk assessment applicable to the process or area being assessed, regardless of the title of the document in which it is recorded. The assessment may form part of the Explosion Protection Document (EPD), exist as a separate study, or be documented in other related explosion-safety records.

In this question, the main task is to confirm that the required assessment has actually been performed, is current, covers the assessed scope, reflects the present way the process is operated, and addresses hazards associated with static electricity. It is also useful to establish which version of the documentation is applicable, where it is available, and whether the way in which it is maintained and updated can be confirmed. The inability to identify a specific person responsible for the document should not, by itself, determine the answer to this question if the existence, scope and currency of the required assessment can otherwise be confirmed reliably.

After technical, material or organisational changes, check whether the scope and assumptions of the assessment still correspond to the actual process. Where start-up, shutdown, filling, emptying, cleaning, or foreseeable and rare malfunctions are also relevant to the assessed scope, check whether the corresponding process states are included in the assessment.

At this stage of the audit, do not yet determine in detail during which specific activities electrostatic charge is generated, accumulated or discharged, whether a possible discharge can constitute an effective ignition source, or which protective measures are required. These matters are verified in subsequent audit questions.

Significance of the Explosion Risk Assessment for the EPD

Under § 7(1) of the Polish Regulation of the Minister of Economy of 8 July 2010, before making a workplace available for use, the employer prepares an Explosion Protection Document (EPD) on the basis of the risk assessment referred to in § 4(4) and (5).

The EPD documents the results of the assessment and the explosion-safety arrangements arising from it. Under § 7(3), it should in particular include a description of the protective measures applied, a list of hazardous areas together with their zone classification, and the employer’s declaration including, among other things, confirmation that the risk assessment has been performed and the review intervals for the protective measures used.

A properly performed and current Explosion Risk Assessment therefore provides the basis for subsequent conclusions documented in the EPD. If the assessment does not reflect the actual process, omits significant hazards, or has not been updated following changes relevant to explosion safety, the reliability of the resulting conclusions concerning hazardous zones, ignition sources and protective measures also requires re-verification.

Employer responsibilities

Carrying out the risk assessment associated with the possible occurrence of an explosive atmosphere and preparing the Explosion Protection Document (EPD) on that basis are responsibilities of the employer. The assessment should cover, among other things, the possible occurrence of an explosive atmosphere and the occurrence and activation of ignition sources, including electrostatic discharges, as well as the installations used, substances and mixtures, processes, their interactions and the possible consequences of an explosion.

On the basis of the completed assessment, the employer prepares the EPD before making the workplace available for use. The document should reflect the results of the assessment and the resulting safety requirements, including, among other things, the protective measures applied, the classification of hazardous areas and the rules for their safe use.

The employer is also responsible for ensuring that workplaces, equipment and work organisation correspond to the conclusions arising from the risk assessment and the EPD, and that the documentation is updated when changes to the workplace, equipment or work organisation may affect explosion safety.

The documentation should lead to the actual location in the process

The fact that static electricity is addressed in the Explosion Risk Assessment (ERA) is only the starting point. Further assessment requires determining where in the actual process the electrostatic hazard is relevant — in which area, installation, process node or process stage.

On the basis of the ERA entry, the auditor should be able to identify in the plant the specific place, installation or process stage to which the identified hazard applies and then verify that scope in the field.

The assignment does not have to follow organisational department boundaries or use one prescribed form of presentation. It may be documented in an ERA table, an installation description, a process flow diagram, an area plan, an equipment list or several linked documents. What matters is that the assessment findings can be linked unambiguously to the actual location and the current process configuration.

Hazardous-area classification and electrostatic-hazard assignment describe different information

Hazardous-area classification identifies spaces in which an explosive atmosphere may occur with a defined frequency and duration. Assigning electrostatic hazards answers a different question: in which parts of the process do electrostatic phenomena require further assessment as a potential ignition source.

Within one Ex zone, different items of equipment and operations may have different electrostatic significance. Conversely, one process operation may involve several items of equipment, material-transfer points or parts of an installation. Hazardous-area classification and electrostatic-hazard assignment therefore serve different functions. This question does not repeat hazardous-area classification; it checks whether the ERA provides a sufficiently precise basis for identifying the parts of the process that require further assessment.

The level of detail should support further assessment

A statement such as “electrostatic hazard exists in production” or “in Ex zones” is usually too general if it does not show which installations or process stages are subject to further requirements. On the other hand, the documentation does not need a separate entry for every individual component where the scope is unambiguous and the assessment boundaries can be clearly derived.

A practically useful assignment makes it possible to identify, for example, a specific process section, filling or emptying station, material-handling node, process vessel, filtration system, transfer point or another part of the installation for which relevant activities, possible ignition sources and required protective measures can subsequently be assessed.

The importance of boundaries and interfaces between process stages

The hazard may relate not only to one item of equipment but also to a material-transfer interface between items, an interface between fixed and mobile equipment, a temporary configuration or a process state other than normal production. The assignment should therefore follow the actual material flow and operating method rather than only room or equipment names.

If the process has been modified, equipment or materials have changed, work organisation has changed or the material flow has been altered, the previous assignment may need to be reverified. An outdated hazard map may cause further assessment to be carried out for the wrong scope.

Role of this question in the audit logic

This question primarily answers “where?”. It does not yet determine in detail “during which activity?” charge is generated or accumulated, whether a possible discharge can become an effective ignition source, or which protective measures are required. Those matters are developed in subsequent stages of the audit.

Documentation and the actual way the work is performed

Documentation used when performing work is the practical translation of requirements arising from the risk assessment into the way specific activities are carried out. Requirements for protection against electrostatic hazards do not have to be contained in a single document or in a document with a specific title. They may be contained, among other things, in workstation and process instructions, operating procedures, process descriptions, work-preparation rules, equipment documentation, or separate requirements concerning protection against static electricity.

What matters is not so much the title of the document, but whether persons performing the activity have clear rules that are appropriate to the actual working conditions. Where the hazard assessment requires specific rules for protection against static electricity, those requirements should be translated into the documentation used during the work in a way that is understandable and practicable.

The documentation should reflect the current process, materials used, equipment, work organisation and the actual sequence of activities. The mere existence of an instruction or procedure does not by itself confirm that the applicable requirements have been effectively implemented. A document may be formally current yet still fail to reflect the actual way the work is performed or changes introduced into the process.

Differences between documentation and practice may develop gradually. They may result, among other things, from changes in equipment or materials, changes in work organisation, introduction of new ways of performing activities, operator experience, arrangements adopted after modernisation, or an established way of working that over time has begun to differ from what is described in the documentation. For this reason, consistency between documentation and actual work should be assessed not only from the document text but also against the current process.

Clarity of requirements is particularly important. General statements such as “apply static-electricity protection rules” or “provide earthing” may be insufficient if the documentation does not make clear which activity the requirement applies to, when it must be used and what method of working is required in practice.

Consistency in the way the same activity is performed by different persons and on different shifts is equally important. If the way work is performed depends primarily on the experience of a particular operator and the required rules have not been clearly defined and established in the applicable documentation, a gap may develop between the formally adopted method of work and actual operating practice.

The currency of documentation is particularly important following technical, material, process or organisational changes. A change in working conditions may mean that requirements that were previously appropriate no longer reflect the actual process. Work documentation should therefore remain linked to the current state of the process and to the results of the applicable hazard assessment.

This question assesses whether the documentation is consistent with the actual way the work is performed and whether electrostatic-hazard protection requirements have been properly translated into operating practice. It does not yet assess in detail the technical effectiveness of individual protective measures or the mechanisms of electrostatic charge generation and dissipation. Those matters are developed in subsequent audit questions.

The process activity as the location of electrostatic phenomena

Electrostatic charge is generated primarily through contact and separation of materials and in processes involving relative movement of surfaces, flow, size reduction, transfer, filtration, spraying or other mechanisms that promote charge separation. Identifying only an area or item of equipment is therefore insufficient; further assessment requires identifying the specific activities and process states during which an electrification mechanism may occur.

The actual operating sequence matters. The same material may behave differently during static storage, pneumatic conveying, transfer, container filling, filtration or installation cleaning. The same installation may also present different electrostatic conditions depending on how it is operated.

The level of detail should reflect changes in mechanism or conditions

There is no need to divide the process into every individual operator movement. It is useful, however, to distinguish operations or stages in which the material, contact and separation mechanism, flow, velocity, geometry, filling or emptying method, type of equipment or another condition relevant to charge generation, accumulation or dissipation changes.

Typical examples include liquid transfer through piping, transfer between vessels, top filling, filtration, atomisation, transfer of powders or granules, pneumatic conveying, mixing, silo discharge, filling and emptying packages, unwinding film and other operations involving intensive contact and separation of materials.

Periodic activities and states other than normal production

Electrostatic hazards may also arise during activities performed infrequently or outside the normal production cycle. Sampling, cleaning, blockage removal, removal of residual material, maintenance, process start-up and shutdown, or the use of temporary equipment may create conditions different from steady-state operation.

Where such activities are foreseeable and form part of the actual operating method, they should be included when identifying activities relevant to electrostatic hazards.

Identifying the mechanism is not yet an assessment of ignition capability

Finding that charge may be generated or accumulated during an activity does not automatically mean that an effective ignition source will occur. Relevant factors include the possible discharge type, material properties, grounding and charge-dissipation arrangements, geometry and the conditions under which an explosive atmosphere is present.

The purpose of this question is to identify correctly the activities requiring further assessment. Determining whether the identified phenomenon can lead to an effective ignition source and which protective measures are required belongs to subsequent stages of the audit.

How do legislation and standards address ignition sources?

ATEX Directive 1999/92/EC — workplace explosion-risk assessment

The Directive on the protection of workers exposed to risks from explosive atmospheres requires the risk assessment to consider not only the likelihood and persistence of explosive atmospheres, but also the likelihood that ignition sources — including electrostatic discharges — will be present and become active and effective. Installations, substances used, processes and their possible interactions are also considered, and explosion risks are assessed overall.

This distinction is important. Merely establishing that static electricity may occur in a process does not determine whether an ignition hazard exists. The assessment should address the actual scenario in which an explosive atmosphere and an ignition source may be present at the same time under conditions capable of leading to ignition.

The same logic is reflected in Polish requirements for explosion-risk assessment, which likewise require the likelihood of ignition sources, including electrostatic discharges, to be considered together with their activation.

PN-EN 1127-1 — general methodology for explosion prevention

PN-EN 1127-1:2019-10 provides a general methodology for identifying and assessing hazardous situations that may lead to an explosion and for reducing risk. It therefore provides a broad reference for identifying ignition sources and assessing their significance in explosion safety.

In practice, ignition sources should be considered in relation to the ignition capability of the specific explosive atmosphere, rather than solely on the basis that a particular physical phenomenon is present. The possibility of that ignition source occurring under the conditions being assessed must then also be considered.

The methodology also structures ignition-source assessment according to the conditions in which a source may occur. Depending on the case, normal operation, foreseeable and rare malfunctions are considered where they are relevant to the occurrence or activation of an ignition source.

IEC TS 60079-32-1 — electrostatic hazards

IEC TS 60079-32-1:2013+A1:2017 is a detailed technical document devoted to hazards arising from static electricity. It can be used in the assessment of electrostatic hazards and describes equipment, product and process properties relevant to avoiding ignition and electrostatic shock hazards caused by static electricity.

The document covers, among other matters, earthing of conductors, reduction of charging, restriction of chargeable insulating areas, the behaviour of liquids and bulk solids, charging of people, and types of electrostatic discharge. Its purpose is to reduce the likelihood of hazardous electrostatic discharges in an explosive atmosphere to an acceptably low level.

It also illustrates why charge generation, charge retention or accumulation, the possibility of a discharge occurring, and the ignition capability of that discharge are not equivalent concepts. Different electrostatic discharge types do not necessarily have the same ignition capability.

PN-EN ISO 80079-36 — potential and effective ignition sources

PN-EN ISO 80079-36:2016-07 primarily concerns non-electrical equipment intended for explosive atmospheres and requires a formal ignition-hazard assessment. It is not a standard for carrying out the Explosion Risk Assessment of an entire workplace, but it provides a particularly useful structure for ignition-source terminology.

Within the equipment methodology used by this standard, successive levels can be distinguished:

possible ignition source → a phenomenon or type of source whose occurrence has to be considered;

potential ignition source → an equipment-related source that has the capability to ignite an explosive atmosphere;

effective ignition source → a potential ignition source considered additionally in terms of when it can occur and become effective, for example in normal operation, expected (foreseeable) malfunction or — for the relevant level of protection — rare malfunction.

This distinction is particularly important for electrostatics. Not every possibility of charging constitutes a potential ignition source, and not every potential ignition source necessarily becomes an effective ignition source in the assessed scenario.

What does this mean for electrostatic hazards?

The electrostatic-hazard assessment should determine whether, under the actual process conditions, an electrostatic discharge capable of igniting the specific explosive atmosphere can occur and whether such a scenario can realistically arise.

It is therefore not enough to state that static electricity is present or that materials, people or equipment can become charged. The assessment has to consider how charging occurs, whether a particular discharge type can arise, and the properties of the explosive atmosphere with which that discharge may come into contact.

Both the characteristics of the discharge and the properties of the material or mixture forming the explosive atmosphere are relevant. For dusts, one important parameter may be minimum ignition energy (MIE); ignition sensitivity may also be affected by particle size, moisture, composition, additives and other material properties. The data used in the analysis should therefore be representative of the material actually present in the process.

Not every possible electrostatic discharge has the same ignition capability. Different discharge mechanisms may have different significance depending on process conditions and the properties of the explosive atmosphere. The assessment should therefore not be reduced solely to the presence of charge or to a simple comparison between one energy parameter and one material value.

It is also important to determine whether a potential ignition source can become effective under the conditions concerned, meaning whether it can actually occur in a scenario in which an explosive atmosphere is present at the same time. Depending on the case, normal operation, foreseeable malfunctions and — where required — rare malfunctions may be relevant.

A properly performed analysis may therefore conclude either that a particular electrostatic phenomenon is a significant ignition source or that the scenario can be excluded on a documented basis. Excluding the hazard is not itself a deficiency; what matters is whether the conclusion has an appropriate technical basis and corresponds to the actual process conditions.

The presence of static electricity alone therefore does not establish the presence of an effective ignition source.

Boundary of the preliminary audit

As part of the preliminary audit, the auditor does not repeat a specialist ignition-source analysis, independently determine discharge energies or MIE values, or replace the appropriate technical assessment. The auditor verifies whether the appropriate analysis has been performed, whether it corresponds to the actual process conditions and whether the conclusion reached has an appropriate documented basis.

Protective measures against electrostatic hazards

Protective measures should arise from the previously identified hazard and correspond to the particular scenario in which an electrostatic phenomenon could lead to ignition of an explosive atmosphere. There is no single universal measure that is appropriate for every process, material and type of possible discharge.

ATEX Directive 1999/92/EC requires technical and/or organisational measures appropriate to the nature of the operation, following the priority of preventing the formation of explosive atmospheres, avoiding their ignition and — where necessary — mitigating the effects of an explosion. PN-EN 1127-1:2019-10 presents explosion safety as a process of risk assessment and risk reduction using appropriate preventive and protective solutions.

The protective measure must correspond to the hazard mechanism

For static electricity, it is important to understand which part of the scenario the applied measure acts upon. A measure may reduce charging, provide safe dissipation of charge, prevent hazardous potential differences, restrict chargeable insulating surfaces, or reduce the possibility of a particular type of discharge occurring.

IEC TS 60079-32-1:2013+A1:2017 identifies, among the basic approaches to controlling static electricity, earthing of conductors, reduction of charging and restriction of chargeable areas of insulators. A solution that is appropriate for an isolated metallic item therefore need not be appropriate for an insulating surface, a flowing liquid, bulk solids, an FIBC or charging of a person.

Earthing and equipotential bonding — fundamental, but not universal

For conductive items, earthing and equipotential bonding are fundamental protective measures, but they perform different and complementary functions. Equipotential bonding limits potential differences between conductive items, while earthing provides a path for charge to dissipate to earth.

Earthing does not prevent charge from being generated and it is not a solution to every electrostatic problem. For insulating materials or other hazard mechanisms, different solutions may be required, such as reducing charging, selecting suitable materials, restricting insulating surfaces or — in appropriate applications — ionisation.

Electrostatic protection is a system

In many processes, protection depends on several elements working together. One example is charge dissipation from a person through the person–footwear–floor–earth system. Likewise, technical solutions may need to be complemented by organisational rules, the correct sequence of operations, training, monitoring or process interlocks.

The presence of one individual measure — for example an earthing conductor, footwear with specified properties or an ioniser — should therefore not automatically be equated with full control of the hazard. Effectiveness depends on the complete solution operating under the conditions for which it was intended.

Effectiveness must be maintained

A correctly selected measure can lose effectiveness over time because of wear, corrosion, contamination, damage, changes in material properties or changes to the process. Protection against electrostatic hazards therefore does not end with one-time implementation: depending on the solution, inspections, measurements, functional tests and reassessment after changes may be required.

Detailed technical criteria, measurement values and inspection frequencies should arise from the relevant assessment, technical documentation and applicable standards and guidance; a single limit value should not be treated as universal for every measure and process.

Further information in the guide

Detailed principles for earthing and equipotential bonding, transfer of liquids and bulk solids, floors, footwear and clothing, ionisation, FIBCs, inspection and measurement, operational practices and earth-monitoring systems are described in the guide “Protection against static electricity in industrial installations”.

Organisational measures for controlling electrostatic hazards

Protection against electrostatic hazards is not based solely on technical solutions. ATEX Directive 1999/92/EC explicitly requires technical and/or organisational measures appropriate to the nature of the operation. Annex II also addresses worker training and — where required by the explosion protection document — written instructions and a permit-to-work system for specified activities.

Instructions, procedures, a defined sequence of operations, work-preparation rules, supervision, training or a permit-to-work system can therefore be genuine organisational protective measures when they arise from the hazard assessment and reduce the likelihood of a hazardous scenario.

A procedure should arise from risk assessment

HSE notes that procedures are agreed safe ways of doing work, but their use should be informed by risk assessment. They should not automatically be treated as the only barrier where a more reliable technical solution can more effectively reduce the opportunity for human error. Well-designed technical and organisational measures normally complement one another.

If safety depends, for example, on connecting earthing before transfer starts, following a defined sequence or using specified equipment, that requirement should be translated into an unambiguous way of performing the work.

Procedures and competence are linked

Issuing an instruction alone does not make an organisational measure effective. HSE emphasises that procedures do not replace competence, and training alone is not sufficient evidence of competence. What matters is the combination of knowledge, skills and experience and the ability to apply the requirement correctly during actual work.

This is particularly important for infrequent activities, non-routine situations and contractor work, where local requirements may not be obvious.

Link to the guidance

The practical role of procedures, training and supervision within the protection system is developed in the guide “Protection against static electricity in industrial installations”, particularly in chapter 12 “Operational practices” and chapter 13 “Responsibilities and roles in electrostatic-hazard control”.

Earthing and equipotential bonding — different functions

In electrostatic-hazard control, earthing and equipotential bonding perform different but complementary functions. Equipotential bonding limits potential differences between conductive items, while earthing provides a path for charge to dissipate to earth. The guide notes that a connection to earth alone does not solve the problem if hazardous potential differences can still arise between conductive parts.

Electrically isolated conductive items are especially important

A conductive object that is electrically isolated from earth can accumulate charge and reach a potential capable of producing a spark discharge. IEC TS 60079-32-1 and recognised industry guidance therefore emphasise electrical continuity for conductive items that can become hazardously charged in the process concerned.

The entire conductive path matters. Coatings, corrosion, contamination, loose joints, insulating supports or configuration changes can cause an item that is assumed to be “metal and earthed” to become electrically isolated in practice.

Earthing is not a universal measure

Earthing conductive parts does not prevent charge generation itself and does not automatically control hazards associated with insulating materials, plastic surfaces, some liquids or bulk solids. Other measures may be required according to the hazard mechanism.

A single resistance criterion should not be transferred to every application. Acceptance values, the connection method and the need for monitoring should follow from the relevant technical document, the type of object and the process scenario.

The connection must be present when it is needed

For transfer operations, the presence of a conductor or clamp is not enough; the operating sequence also matters. HSE guidance on flammable liquids emphasises making required connections before flow begins and maintaining them effectively during the operation. Detailed arrangements and technical criteria are described in chapter 4 of the guide.

Inspection, measurement and functional testing are not the same thing

The verification method should correspond to the function of the protective measure. In one case visual inspection and checking mechanical condition may be sufficient; in another, continuity or resistance measurement may be required; and for a monitoring system, a functional test may be needed to check the response to an actual or simulated loss of the required state.

One type of protocol or one type of measurement should therefore not be expected for every electrostatic-protection measure.

What may require periodic verification?

Depending on the adopted protection system, this may include:

• earthing paths and equipotential connections;
• leads, clamps and connection points used during operations;
• conductive or dissipative hoses and other items whose electrical continuity is important;
• earthing-monitoring systems, alarms and interlocks;
• ionising devices;
• floors and the person–footwear–floor system where they form part of the adopted protection;
• other devices, materials or solutions whose properties may deteriorate during service.

Detailed assessment of personnel protection, footwear, flooring and clothing is carried out in question 12.

There is no single frequency appropriate for every measure

Do not automatically assume a “once a year” rule. For protective measures used in connection with explosion hazards, the dates of systematic reviews should be defined by the employer and stated in the Explosion Protection Document. After changes that may affect the effectiveness of protection, prompt review and verification are required.

Frequency may also follow from technical documentation, the manufacturer’s instructions, an adopted standard, the risk assessment or the nature of service. A measure exposed to frequent disconnection, corrosion, contamination or intensive wear may require more frequent inspection than a solution operating under stable conditions.

Electrical-installation inspection is not the same as full verification of electrostatic protection

Polish Building Law requires an inspection of electrical and lightning-protection installations at least once every five years, including, among other things, the condition of connections and the earthing of installations and apparatus. Such a protocol can be important audit evidence, but it does not replace all inspections of electrostatic-protection measures arising from the process, the Explosion Protection Document or the adopted protection concept.

For example, a five-year electrical-installation inspection does not automatically confirm the current condition of a clamp used to earth a drum, a conductive hose, an earthing-monitoring system or other process-related protective solutions.

Test conditions can matter

For some electrostatic properties, the result depends on the conditions under which the test is performed. Relevant factors may include humidity, temperature, surface condition and cleanliness, configuration of the tested system and the way electrodes are applied or the instrument is connected.

A preliminary auditor does not need to independently judge the correctness of a specialist measurement method, but should check whether the documentation makes it possible to establish how the test was performed and which criterion was used to evaluate the result.

A single satisfactory result does not mean permanent effectiveness

A measurement confirms the condition of a measure at a particular point in time. Where properties can deteriorate over time, systematic verification matters.

Comparing results with earlier measurements may also reveal a deteriorating trend before a limit criterion is exceeded. This does not mean trend analysis is mandatory for every measure; it should be used where it provides meaningful information.

Monitoring systems also need to be checked

A monitoring system can supervise an earthing condition or another parameter during the operation itself and indicate its loss. Where the system operates with an alarm or process interlock, periodic verification should confirm not only that the device is present but also that it performs the required function.

The absence of an alarm is not by itself evidence that the system will correctly detect a real abnormal condition.

A technical change can have a significant effect on electrostatic hazards

A change does not have to involve rebuilding the whole installation. Replacing a hose, gasket, liner, coating or a metal component with a plastic one may alter electrical continuity, the charge-dissipation path or the possibility of charge accumulation.

Process parameters can also matter: flow velocity, pneumatic-conveying rate, free-fall height, product-entry geometry, mixing speed or dosing rate. Changing these parameters may increase charge generation or accumulation and affect the effectiveness of previously adopted safeguards.

Material changes also require attention

A change in raw material, formulation, moisture, additive, packaging, FIBC type, supplier or cleaning agent may be relevant where it changes properties important to electrostatic hazards. A formally minor material change may therefore require previous assumptions to be checked again.

Work outside normal operation may create a different hazard configuration

Maintenance, cleaning, blockage removal, sampling, emergency emptying or temporary equipment can alter the installation configuration for a limited period. Temporary hoses, pumps, containers, open equipment, disconnected sections, bypasses or contractor equipment may appear. Under these conditions, both charge generation and accumulation and the available dissipation paths may change.

A temporary change is still a change

If a temporary arrangement changes material, installation configuration, process parameters or protective measures, its effect on electrostatic hazards should be assessed before use. Where relevant, the conditions for its use and restoration of the intended state should also be defined.

Management of Change (MOC)

Many sites assess changes through a Management of Change (MOC) system. The existence of an MOC form is not evidence of an adequate assessment. What matters is whether the actual change was evaluated for its effect on electrostatic charge generation, accumulation and dissipation and on the effectiveness of existing protective measures.

The assessment should lead to specific actions

If a change affects previous assumptions, it may require updates to the explosion risk assessment, explosion protection document, instructions, process parameters, earthing and equipotential bonding, monitoring, inspection scope or information provided to personnel. The assessment alone is insufficient if its conclusions are not implemented before work or operation starts.

Boundary of the preliminary audit

The auditor does not repeat the specialist technical assessment of a change. The audit checks whether the change was identified and assessed before implementation, whether appropriate competent persons performed the assessment, and whether the outcome was translated into actual protective measures and working arrangements. Where specialist analysis is needed, that requirement should arise from the change-assessment process.

Loss of a protective measure changes the safety conditions of the process

Where the adopted protection concept relies on a particular protective measure, its absence or loss of effectiveness means that process safety can no longer rely on the previous assumptions.

Examples include failure to confirm earthing of a tanker, IBC, drum or Type C FIBC; a broken or disconnected equipotential bonding connection; damage to a cable, clamp or connection point; loss of the required electrical continuity of a hose; an earthing-monitor alarm; failure of a required interlock; a verification or measurement result outside the acceptance criterion; or damage to another protective measure.

These situations do not all require an identical response. The required action should follow from the function of the measure and the relevant hazard scenario.

An alarm or monitoring system detects a condition but does not remove its cause

A monitoring system may detect loss of a required connection and generate an alarm or interlock the process. This does not mean that the cause of the abnormality has been removed.

Resetting an alarm should not replace determining why the system failed to confirm earthing. If the cause is an unsuitable connection point, contamination, cable damage or lack of actual continuity, simply restarting the system does not restore the protective function.

The operator should know the limits of their decisions

A person performing the work does not need to diagnose the technical cause independently or carry out a specialist assessment of the effectiveness of the solution. They should, however, know when not to start or when to stop work, how to bring the activity to the required safe state, whom to notify and what must not be done until the issue has been resolved.

Technical assessment and the decision to release the process for further operation should belong to the person or function with the appropriate competence and authority under the site's organisation.

A substitute measure must not be improvised

If a required protective measure is unavailable, it should not automatically be replaced by another solution simply because it appears similar.

An additional cable, different clamp, temporary hose or manual check in place of a failed interlock should be used only where its function and conditions of use have been properly assessed. If such a solution changes the way the process is operated or the adopted protective measures, its assessment should also be linked to the change-management principles addressed in question 10.

Safe restart requires confirmation that the protective function has been restored

Removal of a visible symptom does not necessarily mean that the cause has been removed.

After repair of a cable, replacement of a clamp, correction of a monitoring-system fault or another intervention, it may be necessary to reconfirm the effectiveness of the measure. The required verification should follow from the nature of the solution.

Periodic inspections, measurements and tests are assessed in question 9. This question checks whether, following a specific abnormality, the process is prevented from restarting until the required state has been confirmed.

Events and abnormalities are also sources of information

Repeated alarms, damaged clamps, loss-of-continuity events, failed verification results or unexplained electrostatic discharges may indicate a problem wider than an individual defect.

Where the same abnormality recurs, simply restoring the process to operation each time may be insufficient. The technical, organisational or process cause and the need for further analysis should be considered.

Footwear and flooring form one system

Where charge is dissipated from a person through footwear and flooring, both components must provide an appropriate path to earth. Suitable footwear will not be effective on an insulating surface, and suitable flooring will not provide the intended protection if footwear electrically isolates the person from the floor. Therefore, the description “antistatic footwear” or “antistatic flooring” alone does not confirm effectiveness of the complete system.

10⁸ Ω and 10⁹ Ω do not mean the same thing

Documentation may contain limits of 10⁸ Ω and 10⁹ Ω. They arise from different requirements, test methods and applications and should not be used interchangeably. In approaches used to control electrostatic ignition hazards, a limit in the order of 100 MΩ (10⁸ Ω) is commonly encountered for a charge-dissipation path through footwear and flooring. By contrast, footwear classified as antistatic under product standards may have resistance up to 1000 MΩ (10⁹ Ω). Footwear can therefore satisfy a product-level “antistatic” requirement and still fail the criterion adopted for a specific electrostatic ignition protection system.

Before assessing a result, establish what was measured, by which method, in which configuration and against which criterion.

The test method matters

The properties of footwear alone, floor resistance to earth or point-to-point resistance, the footwear–flooring combination with a person, and charge dissipation under conditions of use can all be tested separately. Results obtained by different methods should not be compared directly merely because they are all expressed in ohms. IEC 61340-4-5 specifically addresses footwear and flooring in combination with a person.

Actual conditions can change effectiveness

The charge-dissipation path can be affected by worn or contaminated footwear, insoles and overshoes, floor contamination or repairs, mats and coverings, coatings, maintenance products and environmental conditions. An entry tester may confirm a particular path through the person and footwear to the tester electrode, but it does not automatically confirm the properties of the workplace flooring.

Protective clothing is assessed according to its electrostatic function

Clothing does not replace the person–footwear–flooring–earth charge-dissipation path. It is a separate protective element intended to limit ignition-capable discharges associated with charge on the clothing material or its components.

EN 1149-5 specifies material and design requirements for electrostatic dissipative protective clothing. Material properties may be assessed, among other methods, by surface resistance according to EN 1149-1 or by charge decay according to EN 1149-3. For example, a surface-resistance criterion may be ≤ 2.5 × 10⁹ Ω, while charge-decay assessment uses criteria such as t₅₀ < 4 s or shielding factor S > 0.2. These values relate to a different function and test method from the 10⁸ Ω criterion applied to the person-to-earth path and should not be compared directly.

The auditor should confirm the applicable requirement for the actual clothing model, how it is worn, and the relevant use and maintenance conditions. The description “antistatic clothing” alone is not sufficient evidence.

Operational knowledge does not mean expert knowledge

ESH-01 is a preliminary audit. Persons performing the work should not be expected to calculate discharge energy, determine minimum ignition energy, classify discharge types or perform a specialist ignition-source assessment. The required level of knowledge should correspond to the person’s actual tasks and responsibilities.

Understanding operating conditions matters more than definitions

A person should know which stages of the activity are subject to electrostatic requirements, which measures and conditions must be provided before and during the work, what their function depends on, and which items of equipment, materials, parameters or configurations must not be changed arbitrarily. The important point is recognising the boundary beyond which the existing safe-working assumptions can no longer be relied upon.

Knowledge should include foreseeable deviations

Particular attention should be paid to infrequent activities, restart, cleaning, maintenance, changes of material or equipment and other foreseeable departures from normal operation. Question 13 checks whether the person recognises the limits of normal operating conditions. The formal management of change system is assessed in question 10, while response to loss of a required protective function is assessed in question 11.

Training records are supporting evidence

Legislation requires appropriate training in explosion protection, but a record of attendance does not by itself confirm practical understanding. The most useful verification is a short discussion linked to the actual operation, compared with the documentation and the observed way of working.

Immediate response and closure of the problem are different stages

After a nonconformity is identified, work may need to be stopped or not restarted, the installation made safe and the problem reported. This question assesses the subsequent stage: detection → recording → assessment → action → responsibility → implementation → effectiveness verification → closure.

Effectiveness verification should match the function that was lost

Not every nonconformity requires a measurement. Appropriate evidence may be a resistance or continuity measurement, a functional test of monitoring or an interlock, technical inspection of a repaired component, repetition of a previously failed test, or verification of the actual work practice. The method should correspond to the function affected by the nonconformity.

Not every fault requires a formal root-cause analysis

The depth of assessment should be proportionate to the problem. A single fault may require a straightforward technical action and verification. However, recurring damage, alarms or failed results should prompt consideration of a broader technical, operational or organisational cause.

Temporary solutions require control

A temporary measure should be clearly identified as temporary, have defined conditions of use and remain controlled until a permanent solution is implemented. If it changes the process configuration or the way a protective measure functions, it should be appropriately assessed before continued use.