C-DRONE GUIDE · 25 JULY 2026
Tank, boiler and confined space inspection by drone: method, safety, price
Sending a technician into a tank, a boiler or a ventilation duct is one of the most tightly controlled operations in industry: potentially oxygen-depleted atmosphere, narrow access, zero lighting, a mandatory attendant outside, entry permits, sometimes full internal scaffolding. Every entry avoided is a risk avoided and hours of downtime saved. That is exactly what caged indoor drones offer: a protective cage, powerful onboard lighting and GPS-free navigation let them fly inside a closed volume and bring back complete inspection imagery while everyone stays outside. Here is how a confined space drone inspection unfolds, what the regulations say, and what it costs in 2026.
Published on 25 July 2026, reviewed on 31 July 2026 — regulations in force as of July 2026.
Why confined spaces are ideal drone territory
In a confined space, the cost of inspection does not come from the inspection itself but from everything deployed so a human can enter safely: complete draining and gas-freeing, atmosphere testing, entry permits, a dedicated attendant, harnesses and rescue means, often internal scaffolding to reach the upper sections. In a power plant boiler or a large storage tank, erecting and dismantling the scaffolding alone can add several days of downtime.
The caged drone bypasses most of that apparatus: it enters through a manhole, flies in contact with the walls thanks to its cage, and its tiltable camera with onboard lighting documents welds, coatings, refractory linings and corrosion. Feasibility was demonstrated early: as far back as 2013, an ETH Zurich team (Nikolic, Burri, Rehder, Leutenegger, Huerzeler and Siegwart) presented at the IEEE Aerospace Conference a research drone navigating by vision and inertial sensing inside a thermal power plant boiler, precisely to replace human inspection from scaffolding (see the study on Google Scholar). Commercial indoor inspection drones have since industrialised the approach.
Tanks, boilers, silos, ducts: what the drone inspects
The scope covers most closed industrial volumes: tanks and reservoirs (petroleum storage, chemicals, food industry) for the condition of coatings, welds and floors; boilers and furnaces for refractory linings, water walls and burners; silos — complementing the external inspection described in our chimneys and silos guide — for internal walls and vaults; ducts, technical galleries and large-diameter pipes, where GPS-free navigation echoes the methods of our tunnel inspection guide. Some aircraft carry, in addition to the camera, an ultrasonic thickness sensor or a LiDAR that renders the volume as a point cloud.
The limit to know: the drone delivers a visual inspection (and dimensional with LiDAR), which is enough for a condition survey, repair targeting or shutdown preparation. When a code or insurer requires certified measurements (thicknesses, non-destructive testing), the drone serves to target the measurement points — contact intervention, human or robotic, remains necessary, but it is shorter and better prepared.
Regulations: outside aviation law, not outside labour law
Like any flight in a fully enclosed volume, indoor inspection falls outside European aviation regulations — the "enclosed space" exemption detailed in our guide on warehouse drone inventory. No open or specific category here; however, operator registration and suitable insurance remain the mark of a serious contractor, and the flight stays subject to all site rules: prevention plan, work permits and, above all, the labour code provisions on confined spaces.
Beware the shortcut, though: "the drone goes in instead of the technician" does not mean "no more constraints". Opening a manhole, atmosphere testing if anyone must approach the opening, and confined-space certifications for any personnel still needed remain the employer's responsibility under its prevention plan. In an explosive atmosphere (a poorly gas-freed hydrocarbon tank), a standard drone is not ATEX-certified: prior gas-freeing remains the rule, exactly as for a human entry.
The price of a confined space drone inspection in 2026
Pricing usually works by intervention day, specialised equipment and report included. Orders of magnitude observed in France in 2026:
| Service | Observed price (excl. VAT) |
|---|---|
| Targeted inspection (one tank or volume, half-day) | €900 to €1,800 |
| Full day (several volumes, same site) | €1,500 to €3,000 |
| Shutdown campaign (several days, detailed report) | €3,000 to €8,000 |
| LiDAR point cloud option for the volume | +€500 to €1,500 |
| Contact thickness measurement option (targeted points) | quoted based on accessibility |
The relevant comparison is not with another drone service but with the scenario avoided: internal scaffolding, extra days of downtime and human exposure. On a boiler or a large tank, the gap runs to tens of thousands of euros — the same economics as electrical switchboard thermography: the drone's value lies in what it avoids immobilising.
Frequently asked questions about confined space inspection
Does the tank need to be emptied before the flight? Yes in most cases: the drone flies in the free volume. Gas-freeing remains required if the atmosphere could be explosive, as a standard drone is not ATEX-certified.
Can the drone lose signal inside? Indoor inspection drones are built for this: GPS-free navigation, radio links designed for metallic volumes, and a cage that tolerates wall contact.
Does a drone inspection count for regulatory controls? It documents condition and prepares the controls, but a certified measurement (thickness, NDT) requires contact: the drone targets the points, it does not sign the certificate.
What is the minimum volume size? A standard manhole is enough to get in; in flight, caged aircraft operate in volumes from about two to three metres across, depending on the model.