A dossier technique foudre (DTF) is the mandatory technical study that translates the results of a lightning risk analysis into concrete, sited protection measures for French industrial sites. It is required whenever an analyse du risque foudre concludes that protection is necessary, must reference NF EN 62305 or NF C 17-102, and serves as the legal record inspectors check first.

TL;DR:

  • The DTF must include detailed siting drawings and device specifications, as well as a verification and maintenance schedule, to ensure traceability.
  • The entire process, from ARF to installation and ongoing checks, must be completed within a two-year window for compliance.
  • A qualified organization, typically holding a valid Qualifoudre certificate, must produce and verify the DTF according to referenced standards.
  • Inspections require a complete record, including verification reports and a carnet de bord, to confirm ongoing protection measures.
  • Non-compliance with mandatory documentation and verification procedures can lead to administrative sanctions or activity suspension.
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What a dossier technique foudre contains and why it matters

The DTF is not a design sketch. It is the document that turns the protection level set by the ARF into named devices, drawn locations, and maintenance commitments that an inspector or insurer can audit years later. A well-built dossier reads as a chain: risk level in, device and siting out, verification schedule attached.

A compliant dossier generally includes:

  • Protection measures against direct effects (IEPF): lightning rod type, mesh cage or early streamer emission device, with siting drawings
  • Protection measures against indirect effects (IIPF): surge protective device (SPD) selection, equipotential bonding, and cable separation
  • Grounding and bonding details, including target resistance values where specified
  • A notice of verification and maintenance, and a carnet de bord template for ongoing records

Prefectural model studies, such as the Rhône prefecture’s technical annex, show this same structure: regulatory references, methodology, device lists, plans, and a chapter of recommended actions. Inspectors and insurers treat the DTF, not the ARF alone, as proof that a site has actually acted on its assessed risk.

French regulatory framework: when the DTF is required and which texts apply

The obligation comes from the arrêté du 4 October 2010, as modified by the arrêté du 19 juillet 2011. Articles 16 through 22 define which ICPE rubrics require an ARF and, when that analysis flags a risk, a DTF detailing the measures, their siting, and verification and maintenance arrangements.

The arrêté’s Articles 16 to 23 set out scope, competent organization requirements, ARF and DTF obligations, and carnet de bord duties for listed ICPE installations. That is the operative fact for any site manager trying to confirm applicability: if your rubric is listed, the ARF is mandatory, and the DTF follows automatically whenever the ARF finds a protection need. Our guide on ICPE lightning protection compliance walks through the rubric list in more detail.

French ICPE ARF to DTF compliance sequence

Non-compliance exposes an operator to the same administrative sanctions that apply to other ICPE obligations: formal notice, work orders, or in serious cases suspension of activity, since the DTF is treated as a condition of the operating authorization rather than an optional technical nicety.

Process and timeline: from risk analysis to verified installation

The sequence is fixed by regulation and by the standards it points to. Skipping a step, or doing them out of order, is the most common compliance failure site managers encounter.

  1. Analyse du risque foudre (ARF): conducted first, following NF EN 62305-2 methodology, to determine whether protection is required and at what level.
  2. Dossier technique foudre (DTF): produced once the ARF confirms a need, specifying devices, siting, and grounding.
  3. Installation: must be completed within two years of the ARF’s conclusions.
  4. Initial verification: performed within six months of installation, by an independent competent body.
  5. Ongoing checks: annual visual inspections, full verification every two years, and a post-strike check within one month of any recorded lightning event.

The ARF and DTF are not one-time documents. Any significant change to the site, a revised hazard picture, or a recorded strike should trigger a review of both.

Technical checklist: what the DTF must specify

A tender response or a finished study should let you check off specific technical content, not vague assurances. Treat the following as a minimum.

  • External protection (IEPF): device type (conventional rod, early streamer emission device per NF C 17-102, or mesh cage), siting drawings, and descent conductor routing
  • Internal protection (IIPF): SPD class (Type 1, 1+2, or 2), equipotential bonding points, and conductor separation limits, particularly relevant for sites with photovoltaic installations
  • Grounding: target resistance values where the study specifies them, conductor sizing, and routing plans
  • Documentation: calculation notes, device datasheets, the notice of verification and maintenance, and a carnet de bord template

NF EN 62305-3 covers verification requirements, while NF EN 62305-4 addresses SPD installation for indirect effects. Our technical overview of lightning protection system components breaks down how these elements fit together on a real installation.

Pro Tip:Ask any bidder for a sample DTF before signing a contract. A study that lists devices without siting drawings or a verification schedule is incomplete, whatever the price.

Verification, maintenance, and the carnet de bord you must keep

A DTF without a verification history behind it is close to worthless in an inspection. The regulation is specific about both the cadence and the paper trail.

  1. Initial full verification: carried out by an independent competent organization within six months of installation.
  2. Annual checks: a visual inspection every year to catch obvious degradation, corrosion, or physical damage.
  3. Full verification: a complete technical check every two years, performed by a competent body.
  4. Post-strike verification: required within one month of any recorded lightning strike.
  5. Carnet de bord: must contain copies of the ARF and DTF, every verification report, maintenance actions taken, recorded strikes, and the signature of whoever performed each entry.

Operators are required to keep the ARF, the DTF, the verification notice, and the carnet de bord available for inspection at all times, not just produce them once and file them away. Our piece on insurers’ expectations around the carnet de bord covers how these records factor into claims after a strike.

Choosing who prepares and verifies your dossier

The arrêté requires that both the ARF and DTF be produced by an “organisme compétent.” In practice, Qualifoudre certification is the recognized benchmark in France for firms claiming that competence, referenced across industry and INERIS guidance alike.

Before signing a contract, request:

  • A current Qualifoudre certificate or equivalent proof of competence
  • A sample DTF showing the level of detail you can expect
  • A methodology note naming the standards referenced (NF EN 62305, NF C 17-102)
  • Evidence of independent verification capability, separate from the installation team
  • Proof of professional insurance covering the study and installation work

Treat the absence of any standard reference, a missing carnet de bord deliverable, or no stated verification schedule as a reason to ask more questions before awarding the contract.

INDELEC’s field perspective on common compliance gaps

Working across industrial sites since 1955, INDELEC regularly finds dossiers that name devices but skip siting drawings, or that have no documented protocol for a post-strike check. Both gaps undermine the traceability an inspector is looking for.

A dossier that lists a lightning rod and an SPD but never shows where they sit, or how a strike gets logged, is not a compliance document. It is a shopping list.

A compliant DTF should connect directly to an installation supervision plan and a long-term maintenance contract, not sit as a standalone report that nobody revisits.

The compliance habit that actually protects a site

Most advice on this topic treats the DTF as a box to tick once, filed after the ARF and forgotten until the next inspection. That is the wrong mental model. The dossier is only as good as the verification history attached to it, and a study with a flawless methodology note but no carnet de bord entries is functionally indistinguishable from no study at all when an inspector or an insurer looks at the file after an incident.

DTF file linked to recurring verification records

The conventional advice also under-weights siting drawings. Site managers often assume that naming the right standard and the right device class is the hard part. It is not. The failures we see most often are studies that get the device selection right and then leave the exact location, routing, and separation distances vague enough that nobody on site can verify the installation actually matches the paper.

If you take one thing from this guide, make it this: before you accept a DTF as finished, confirm it includes a signed verification schedule and a carnet de bord template, and confirm the siting drawings are precise enough that a different contractor could install from them without guessing.

— INDELEC

How INDELEC supports your ARF, DTF, and ongoing compliance

INDELEC handles the full sequence under one contract: the analyse du risque foudre and étude technique, installation, and the verification and maintenance program that keeps your carnet de bord current.

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A site assessment typically produces a documented ARF, a DTF with siting drawings and device specifications, and a verification calendar you can hand directly to an inspector. Visit our services page to request a site assessment and get a proposal scoped to your installation.

This article is general information, not a substitute for advice from a qualified lawyer. Consult a qualified legal professional about your own circumstances before acting on anything here.

FAQ

Est-ce que l’étude foudre est obligatoire ?

The étude technique foudre is mandatory only when the prior ARF concludes that protection is required, for ICPE installations covered by the arrêté du 4 October 2010 as modified in 2011. If your site falls under a listed rubric, the ARF itself is always required, and the DTF follows automatically once risk is confirmed.

Quelle est la norme de protection contre la foudre en France ?

French regulation references the NF EN 62305 series for general risk assessment and protective measures, alongside NF C 17-102 for early streamer emission (PDA) lightning rod systems. Both standard families are listed for purchase through AFNOR and are cited directly in prefectural technical annexes.

Qu’est-ce que l’analyse du risque foudre (ARF) ?

The ARF is the risk assessment that must precede any lightning protection study, evaluating the probability and severity of a lightning strike on a given site following NF EN 62305-2 methodology. It determines whether protection is needed and, if so, what level, which the DTF then translates into specific devices and siting.

Est-il obligatoire d’installer un parafoudre ?

A surge protective device (SPD or “parafoudre”) becomes mandatory when the ARF and DTF identify a need to protect against indirect lightning effects, typically for sites with sensitive electrical or electronic equipment. The DTF specifies the SPD type (Type 1, 1+2, or 2) and its installation points as part of the required internal protection measures.

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