C-DRONE GUIDE · 17 JULY 2026
Industrial chimney and silo inspection by drone: method, price and regulations
A 45-metre industrial chimney due for its operating-licence renewal, a grain silo that needs checking before harvest, a refinery flare whose shell has corroded: in all three cases, traditional access — rope-access technicians hanging off the structure, scaffolding erected then dismantled, extended production downtime — weighs heavily on the schedule and on site safety. Industrial inspection drones change the game for the outside of these structures, and sometimes for their inside, provided a specific technical and regulatory framework is respected as soon as an explosive atmosphere comes into play. Here is the method, the prices charged in 2026, and the points to pin down before launching a mission.
Published on 17 July 2026, reviewed on 18 July 2026 — regulations in force as of July 2026.
Chimneys, silos, flares: the limits of traditional access
On a tall structure — a concrete or brick chimney 20 to 100 metres high, a steel or concrete silo, a refinery flare — periodic visual inspection is a requirement, not an option: it conditions the renewal of the operating permit, the insurance policy and, for classified installations, the file submitted to the environmental inspectorate. Historically, two methods have shared the field: rope access, with certified technicians descending the structure section by section, and tubular scaffolding, erected over the full height then fully dismantled after the inspection. Both immobilise the structure for several days to several weeks and represent one of the most closely monitored accident categories in industry: falls from height, falling objects, or a technician feeling unwell partway up a chimney still warm after the furnace was shut down.
Cost follows the same curve as risk. Scaffolding on a 60-metre chimney runs into the tens of thousands of euros for erection and dismantling alone, before the inspection itself even begins; rope access is cheaper but remains slow on a tall structure and only allows a constrained path, hard to combine with a rigorous photographic survey. The drone does not systematically replace these means — physical contact is sometimes still needed for a thickness sounding or a sample — but it handles in half a day almost all of the visual and thermal survey that used to account for half the access budget.
What the drone actually reveals on the structure
The first deliverable is the high-resolution visual survey: on a concrete chimney, optical zoom detects cracks, spalling of the cover concrete and corrosion of exposed reinforcement, degradation of the crown and expansion joints, plus the condition of aviation markings and the lightning conductor. On a steel silo, the visual inspection targets sheet corrosion, the condition of welds and bolted connections, and streaking or wall deformation marks that betray an overload point. Every anomaly is geolocated on the structure and numbered in the report, alongside the matching photo.
The second contribution, less well known, is verticality and deformation measurement: flying a calibrated orbital flight plan around the structure, photogrammetry reconstructs a 3D model that reveals buckling, differential foundation settlement or a progressive lean — precursor signs that a one-off plumb-line survey does not reveal with the same resolution. Thermography, finally, usefully rounds things out: on an operating chimney it reveals an internal refractory defect through an abnormal surface heat signature, and on a silo it picks up a hot spot linked to fermentation or the early stages of combustion in the stored material — an early warning that few traditional methods catch as soon.
The special case of silos: confined spaces and ATEX zones
As soon as a mission touches the inside of a silo or tank holding a combustible material in suspension — flour, grain, sugar, sawdust, certain industrial powders — the atmosphere can become explosive under the ATEX directives: the volume is then classed as zone 20, 21 or 22 depending on how often the dust cloud is present. A standard drone, with unprotected motors and electrical contacts, is a potential ignition source there. The mission can only be carried out with an Ex-certified aircraft — sealed housings, antistatic components, no hot spots — and under a written protocol that first cuts or neutralises the site's ignition sources.
On top of that comes confined-space regulation under labour law: a mandatory prevention plan as soon as an outside company intervenes, a prior risk assessment with the site's HSE team, and often a human standing watch at the access hatch throughout the flight. In practice, most silo missions are limited to the outside of the structure — cladding, roof, hatches, supporting structure — where these constraints do not apply; interior inspection stays reserved for cases where the silo is empty, ventilated and locked out, or handed to an operator specifically equipped and trained for ATEX interventions. Our guide to drone wind turbine inspection details another case where the supporting structure imposes its own flight constraints.
How a mission unfolds and the applicable regulatory framework
A classified industrial site is rarely in a dense built-up area, which simplifies the airspace framework compared with an urban flight: the mission most often runs in the open category, sub-category A3, as long as the site is far from uninvolved third parties — the norm on an enclosed, guarded industrial site. It shifts to the specific category if the structure exceeds 120 metres, if the site sits near an aerodrome or a restricted zone, or if third parties are present in the immediate surroundings: the pilot must then build a SORA file and obtain an operating authorisation before flying. In every case, the operator must be registered on AlphaTango with their FRA number displayed on the aircraft, and covered by aerial liability insurance compliant with Regulation (EC) No 785/2004 — two documents a serious site requires before even signing the quote.
On the ground, the mission is coordinated with the site's safety team: check-in and badge, briefing on exclusion zones (an operating furnace, an active flare, an ATEX zone), coordination with any technical shutdown under way. The flight itself takes one to three hours depending on the height and the number of structures to cover; the report — a photo survey by elevation, thermal overlays where relevant, a 3D model for verticality tracking — is delivered within 5 to 10 working days, including analysis time by a technician trained to read industrial structures. Our guide to the open or specific category details the criteria that shift a mission from one category to the other.
Price of drone chimney or silo inspection in 2026
Prices depend above all on the structure's height, the number of units to cover on the same site, and the deliverables requested (visual only, or visual plus thermal plus 3D model). Ranges observed in France in 2026:
| Mission | Observed price (excl. VAT) |
|---|---|
| Visual inspection of a single chimney or silo (up to 40 m) | €350 to €700 |
| Full inspection (visual + thermal + verticality report), 40 to 80 m | €800 to €1,400 |
| Structure over 80 m, or a site with multiple chimneys / silos | €1,500 to €2,500 |
| Annual campaign across an industrial estate (per structure, tapered) | on quotation |
Compare that with erecting and dismantling scaffolding on a 60-metre chimney, which frequently exceeds €15,000 to €20,000 for access alone, or rope-access technicians billed by the day over several days. The drone does not always remove the need for occasional physical access — a sheet-thickness sounding or a refractory sample remains manual — but it sharply cuts the number of access days needed, and so the length of time the structure is taken out of service.
Frequently asked questions on industrial drone inspection
Does the drone fully replace the rope-access technician? Not always: it covers most of the visual and thermal diagnosis remotely, but a thickness sounding, a material sample or a spot repair still needs physical access. Many sites now combine a drone scouting flight, which then precisely targets where to send a technician.
Does the furnace or flare need to be shut down during the flight? Not necessarily for an external visual survey, but a shutdown or a safe state is often required for fine-grained thermal inspection or any work close to a flame or an intense heat source; this is agreed with the site's safety team before the mission.
How accurate is chimney verticality measurement? A well-georeferenced photogrammetric model reaches centimetre-level accuracy on the structure's overall geometry — enough to catch a lean or a settlement well before it becomes visible to the naked eye.
Can the drone fly inside a closed silo? Only with an Ex-certified aircraft if an explosive atmosphere is possible, an emptied and locked-out silo, and a proper confined-space protocol. In most cases the mission is limited to the outside of the structure, where these constraints do not apply.