Lightning Protection for Manufacturing Halls and Industrial Sites: How the Protection Class Is Determined by Risk Analysis and What It Means for Inspections

The enquiry arrives in a single sentence: “We need a lightning protection inspection for a 60 × 120-metre hall. How much will it cost?” This prompts a question the site manager is not expecting: what protection class was the system designed to, and where is the risk calculation on which that class was based? Silence usually follows at the other end of the line—and then comes the response that the lightning protection system must be there because it is visible from the yard.

For a family home, the owner may often consider this line of reasoning sufficient—although even there, visible conductors and an old inspection report do not in themselves demonstrate the system’s actual condition or prove that nothing has changed since the report was issued. For a manufacturing hall, however, the task is on an entirely different scale: lightning protection is not merely a conductor running around the parapet but a design that takes into account what is manufactured inside, how many people occupy each area, which services enter the building, and what happens if a surge disables the production line’s control system. When the operation or its inputs change, the validity of the entire calculation changes with them. We will explain what belongs in a risk analysis, what LPS Class I to IV changes in the design, why the class alone does not determine the inspection interval, and what to have ready before the technician arrives.

The protection class is determined by risk calculation, not roof area

The starting point is not the size of the hall but an assessment under ČSN EN 62305-2. It compares the calculated risks with the tolerable risk and determines which protective measures are required for the particular building. The result does not necessarily have to be a lightning protection system: the assessment may show that an external lightning protection system (LPS) is unnecessary, or that the risk should be reduced through a combination of measures—shielding, coordinated surge protective devices, changes to service routing, and measures against injury from touch and step voltages. Only where the assessment identifies an external LPS as necessary does the analysis also determine the required lightning protection level (LPL) and the corresponding LPS Class I to IV. This class then affects the entire design: the density of the air-termination system, the number and spacing of down conductors, the earthing arrangement, equipotential bonding, and the calculation of the separation distance from metal and electrical parts.

For an industrial building, the calculation typically considers:

• the dimensions, height, location, and construction of the individual buildings on the site;
• the number and movement of people, outdoor workplaces, and areas where people gather;
• the fire load, combustible materials, and areas with an explosive atmosphere;
• power, data, telecommunications, and measurement services entering the building, including routes between buildings;
• production technology, machine control systems, safety systems, and the consequences of their failure;
• existing air-termination systems, down conductors, earthing, equipotential bonding, and surge protective devices;
• the proposed protective measures and how they have actually been implemented.

The ČSN EN IEC 62305 series is also transitioning to new editions, while the concurrent applicability of a previous edition is defined by its withdrawal date. In practice, this means one thing: the documentation should make clear which edition the designer followed—otherwise, the inspection is comparing the actual installation against an uncertain benchmark. We discuss the changes in the new editions separately.

What Class I to IV means in the design

A lower Roman numeral means more stringent protection. The difference between I and IV is not merely a matter of degree; it changes the requirements for the entire system:

These values come from ČSN EN 62305-3 and are included to show how extensively the class affects the design. Between LPS I and LPS IV, the mesh size increases fourfold and the down-conductor spacing doubles—on a large hall, that can mean many tens of metres of additional conductor and several extra down conductors. The protected volume is verified using the rolling sphere, protective angle, or mesh method; for a complex roof with rooftop structures, only the first method is appropriate.

The most common operational misconception concerns the separation distance s. It is not a constant. It is calculated from the coefficient for the relevant class, the distribution of current between the down conductors, and the material through which the distance extends—and, most importantly, from the length of the path between the point under consideration and the nearest equipotential bonding point. On a tall hall, the required distance at roof level will therefore differ from the distance one metre above ground, and the claim that “a 60 cm clearance is enough” is not valid even as a rough guide. Interestingly, the result can also be improved without modifying the technology: the more down conductors there are, the smaller the share of current carried by each one and the smaller the required s.

An industrial site is not a single building

A combustible-goods warehouse, press shop, administrative unit, transformer station, and outdoor storage tank have different calculation inputs and different consequences of failure. The assessment therefore defines which buildings, zones, and incoming services it covers—and which it does not. A report that does not make clear whether the shelter housing the compressor room was also assessed is of no practical use to the site manager.

Two matters are handled differently on industrial sites than in a detached house. The first is the use of natural down conductors: on a steel hall, structural columns may be used as down conductors if their electrical continuity is documented. With sandwich cladding, however, continuity between the individual panels and connectors cannot be assumed and must not be relied upon without evidence. The second is earthing: large buildings generally use a ring or foundation earth electrode (Type B arrangement), for which ČSN EN 62305-3 recommends an earth resistance below 10 Ω. Connecting the earthing systems of the individual buildings into a meshed earthing network then reduces potential differences along the routes running between them—which are precisely the routes through which surges most readily reach production control systems.

A site with its own transformer station must be assessed as a whole, not building by building

Once a site has its own transformer station supplying several interconnected buildings, it no longer makes sense to order a lightning protection inspection “for Hall No. 2.” The buildings share more than a perimeter fence: they may have a common earthing system, cable routes underground and on cable bridges, and data and control circuits linking different operations. A lightning strike to one building will also affect the others through these routes. The air-termination system, down conductors, earthing, and equipotential bonding must therefore be assessed in the context of the site as a whole. The Type B earth-electrode arrangement and its connection into a meshed earthing network, as described above, are specifically intended to reduce potential differences between buildings. If this interconnection is missing or undocumented, the finding concerns the entire site, not just one building.

The transformer station itself enters the assessment in two ways. As a building, it has its own external lightning protection and its own connection to the site’s earthing and equipotential bonding system—and this is covered by the LPS inspection. The high-voltage section, by contrast, is subject to its own inspection regime and does not fall within the lightning protection inspection. When defining the scope, it is therefore essential to specify in writing what the order includes and excludes.

A new risk assessment under ČSN EN 62305-2 is required whenever a change affects the inputs of the original calculation. On an industrial site, this typically means a change in production technology or building use, an extension or additional storey that changes the geometry and height, new rooftop equipment (PV systems, cooling equipment, ventilation systems, or antennas), or new power, data, or control services between buildings. Risk management is an ongoing task, not a one-off document: if the operation, fire load, number of people, or consequences of a control-system failure have changed since the last calculation, that calculation no longer reflects reality, and the inspection is comparing the installation against an outdated brief.

When requesting an inspection of an industrial site, prepare:

• a list of buildings, including shelters, outdoor technology, and the transformer station, indicating which are to be included in the inspection;
• information about interconnections between the buildings—a shared earthing system, cable routes between buildings, and data and control circuits;
• the risk calculation and LPS design or as-built documentation, if available, together with the latest inspection reports;
• an overview of changes since the last inspection: new technology, extensions, rooftop equipment, and newly installed incoming services;
• site-access conditions, including the need for an access platform, roof access, shutdowns, and escorted access to locked areas.

The LPS class and inspection interval are not the same thing

This is where the overwhelming majority of misunderstandings arise. The risk analysis determines the necessary protective measures and, if an external LPS is required, its LPL and class. The interval between periodic inspections is determined by legislation, using a completely different logic rather than a simple conversion from Class I–IV.

It is worth clarifying the source of this obligation. It does not arise from the standard: under § 4 odst. 1 zákona č. 22/1997 Sb., a Czech technical standard is not generally binding—ČSN EN 62305 is a recognised means of demonstrating compliance, not the source of the obligation itself. The general obligation to maintain and inspect equipment follows from § 4 zákona č. 309/2006 Sb. For lightning protection systems, this is supplemented by the regime for designated technical electrical equipment under zákona č. 250/2021 Sb. and nařízení vlády č. 190/2022 Sb., whose § 7 odst. 5 písm. d) links periodic inspection intervals to příloha č. 4.

For a manufacturing hall, this means the opposite of what is often claimed in practice. Four years is not automatic: příloha classifies buildings intended for production under the three-year interval, areas with a fire or explosion hazard also under the three-year interval, and buildings occupied by more than 200 people under the two-year interval. If the LPS protects critical systems, the interval is two years regardless of the type of building beneath it. Where several applicable intervals coincide for one system, the shortest one applies. The final interval therefore cannot simply be copied from a single table entry; it depends on the particular building, the area in which the equipment is installed, and what the LPS protects.

Moreover, the two- and four-year intervals are identified in příloha as basic maximum intervals, not immutable figures. The supplementary information allows intervals of up to twice that length to be established in a preventive maintenance schedule, but only under the conditions listed in příloha. This is an option for operations with an established and documented maintenance system, not a means of postponing an inspection. The final item of the supplementary information then excludes equipment covered by § 21 odst. 1 zákona č. 250/2021 Sb. from these intervals. However, that provision concerns equipment belonging to the transmission and distribution systems of licence holders and service connections, so it does not apply to a manufacturing hall or industrial site.

The annual visual inspection is the requirement most often overlooked, even though it is not merely a recommendation in a standard. The obligation to carry out a visual inspection at least once a year on every LPS, verifying that the system is not visibly damaged, is stipulated directly by příloha č. 4 nařízení vlády. It therefore runs alongside the periodic inspection rather than replacing it, and a written record should be produced.

Classification as a “critical system” depends on the actual operation and its documentation, not the size of the hall. The fact that manufacturing takes place in a building does not make it a critical system. Equally, the fact that it has been called an “other building” in inspection schedules for years does not make it one. The information “LPS III” is not sufficient on its own to determine the interval. We explain how the intervals differ by building type in our article on lightning protection inspection intervals.

When photovoltaic panels are added to the roof

Panels, ventilation equipment, cooling units, antennas, cameras, cable routes, skylights, and new exhaust outlets—each of these changes the geometry of a roof that the designer may originally have calculated as empty. A structure may extend outside the verified protected volume or move closer to the air-termination system than the calculated separation distance permits. Alternatively—and this is the more troublesome possibility—it may connect the roof to technology inside the hall through DC cables forming loops with an area of several square metres.

Before installation, it makes sense to verify three things: whether the entire installation lies within the protected volume verified using the appropriate method, whether the recalculated separation distance is maintained, and how the change affects equipotential bonding and the coordination of surge protective devices on power, data, and control services. A surge protective device cannot compensate for a poorly designed air-termination system, and the lightning protection system alone will not protect control electronics—the two parts must be designed together. This is discussed in more detail in our article on surge protection in businesses.

After installing substantial rooftop technology, there is little sense in waiting until the next routine inspection. If you are unsure whether the new structure is still inside the protected volume, we can assess it during a lightning protection inspection and tell you immediately whether additional equipotential bonding is sufficient or whether a designer must update the design and risk calculation.

What to prepare before the technician arrives

The inspection technician does not assess only the visible conductors. They compare the actual installation with the design and look for changes made since the last inspection. Without supporting documents, they can only record the current condition and qualify the report because of the limited scope of the assessment.

Prepare:

• the risk calculation, if one exists, and the LPS design or as-built documentation;
• previous inspection reports and records of annual visual inspections;
• the external-influences assessment report; for areas with an explosion hazard, also the written explosion protection documentation under § 6 nařízení vlády č. 406/2004 Sb.;
• a current roof plan showing the PV system, ventilation equipment, antennas, and cable routes;
• a diagram of the earthing, equipotential bonding, and surge protection arrangements;
• a list of structural and technological changes since the last inspection;
• access to the down conductors, test joints, earth electrodes, and roof;
• information about any lightning strike, surge protective device failure, or unusual damage.

An old inspection report cannot replace a missing design—it contains measurement results, not the original design brief. We explain how supporting documentation can be created for a building without records, including what can be surveyed and what must be calculated, in our article on lightning protection documentation for older buildings.

The quotation and report: how to tell whether they cover what you need

The cost of inspecting an industrial site cannot be determined solely from the number of down conductors. It depends on the number and size of buildings, roof complexity, work at height, the number of measurement points, the extent of available documentation, operational restrictions, and the time required to identify changes. A risk analysis or completion of the design is separate professional work, not an add-on to a low-cost periodic inspection.

Before placing the order, obtain a written definition of which buildings and outdoor technologies are included in the price; whether the work is a periodic inspection, an extraordinary inspection, or also includes a design update; who will arrange the access platform, roof access, and any required shutdowns; and how measurement points and identified defects will be labelled in the report. The scope of the inspection technician’s certification also matters—professional competence requirements for work on electrical equipment are governed by nařízení vlády č. 194/2022 Sb., and for areas with an explosion hazard, the certification must also cover that environment.

A usable report identifies the assessed scope and the documents on which the assessment was based, the LPS class and edition of the standard used, deviations from the documentation, inspection and measurement results, and an unambiguous conclusion. A statement that “the lightning protection system is compliant,” without identifying the building or linking the conclusion to the actual installation, will not help the site manager during an official check or an insurance claim.

When to request a new risk calculation

A new risk calculation is always required for a new lightning protection design—and subsequently whenever a change affects the calculation inputs: an extension, a change in the hall’s use, a change in stored substances, a new PV system or other rooftop technology, the installation of new power or data services, or a substantial reconstruction of the production line. The same applies where the original calculation clearly no longer reflects the current condition or the situation needs to be reassessed.

For an older system on which nothing has changed, however, the mere absence of a risk calculation is not in itself a reason to require a new assessment. Such an LPS may have been entirely legitimately designed under the regulations and standards applicable when it was installed, which may not have required the risk calculation used today. The inspection must therefore also assess compliance with the regime that applied at the time, rather than only with current requirements. A new calculation should be requested for a new design, following a relevant change, or where a new assessment is genuinely necessary—for example, where the documentation does not match the actual installation or the operator wants documented evidence that the protection remains adequate.

It is important to keep separate what follows from the calculation and what does not. The LPS class determines the system’s technical parameters—the mesh, down-conductor spacing, separation distance—and the scope of what must be verified during the assessment. The inspection interval is not derived from the class: it is determined by the legal categories in příloha č. 4, the specific building and area, whether the LPS protects critical systems, and the rule requiring the shortest applicable interval.

Sources for this article

• Lightning protection inspections – a service provided by SOHE.
• Lightning protection inspections: how often under ČSN EN 62305 – periodic inspection intervals by building type and what is checked during an inspection.
• Lightning protection documentation for an older building – what information the technician lacks when documentation is unavailable and how it can be completed.
• Surge protection in businesses – why surge protective devices must be designed together with the external lightning protection system.
• Zákon č. 22/1997 Sb. – o technických požadavcích na výrobky; § 4 odst. 1 states that a Czech technical standard is not generally binding.
• Zákon č. 309/2006 Sb. – zajištění dalších podmínek BOZP; § 4 establishes the general obligation to maintain, check, and inspect equipment.
• Zákon č. 250/2021 Sb. – bezpečnost práce v souvislosti s provozem vyhrazených technických zařízení; it covers the regime for designated electrical equipment, inspection technician certification, and § 21 odst. 1 defining transmission and distribution system equipment and service connections.
• Nařízení vlády č. 190/2022 Sb. – vyhrazená elektrická zařízení; § 7 odst. 5 písm. d) and příloha č. 4 specify the basic maximum periodic inspection intervals, the rule requiring the shortest concurrently applicable interval, and the mandatory annual visual inspection of the LPS.
• Nařízení vlády č. 194/2022 Sb. – požadavky na odbornou způsobilost k výkonu činnosti na elektrických zařízeních a na odbornou způsobilost v elektrotechnice.
• Nařízení vlády č. 406/2004 Sb. – prostředí s nebezpečím výbuchu; § 6 governs written explosion protection documentation.
• The ČSN EN IEC 62305 series (Parts 1 to 4) – risk management, protection of structures, and protection of internal systems; the standards are not freely available, so they are listed without links.

This article is for informational purposes and does not constitute legal advice. The specific inspection regime and scope of lightning protection must be established according to the actual operation, the manufacturer’s documentation, the environment in which the system is used, and the risk assessment.

We inspect lightning protection systems on manufacturing halls and industrial sites, defining the scope in advance so that the resulting report does not silently omit half of the buildings—see what the service includes. Send us a non-binding enquiry or email info@sohe.cz, including a description of the site and the documents you have available. We will then tell you whether a periodic inspection is sufficient or whether a designer must first update the design and risk analysis.