Confined space drone inspection in the UK: tanks, silos, boilers and ship holds

For the looking, often. For the work, rarely. Regulation 4(1) of the Confined Spaces Regulations 1997 says no person at work shall enter a confined space to carry out work for any purpose "unless it is not reasonably practicable to achieve that purpose without such entry". HSE's Approved Code of Practice, L101, lists remote visual inspection as one way to avoid entry, but "only if this will provide the same results and safeguards as entry would". That condition is the test a drone inspection has to pass: does it show the inspector what they would have seen, closely enough to make the same decision?

For many internal visual inspections of tanks, silos, boilers, ducts and chimneys it can. For thickness gauging, cleaning, repair or anything that needs a hand on the surface, it usually cannot, and a person or another tool still goes in. BINDT describes remote visual inspection as "a safer alternative to an operator entering a confined space to conduct visual inspection": a safer way to look, not a replacement for every reason to enter.

A caged indoor drone is built to fly in the dark, close to walls, without satellite signals. The cage lets it touch a surface without crashing; onboard lights replace the daylight it will not have; and it positions itself with LiDAR or cameras because satellite positioning is unavailable or unreliable indoors. Those features decide where it fits. The conditions in the space decide the rest.

Some spaces are the wrong job for any drone. A flooded chamber is ROV work; steel plate thickness is magnetic crawler or contact work; a sewer run is usually a pipe crawler; a walk-in tunnel may suit a legged robot. Our guide to confined space inspection robots compares those forms side by side.

Since 1 January 2026 the UK drone regulation has an express rule for enclosed spaces. Article 2A, inserted by the Unmanned Aircraft (Amendment) Regulations 2025, says the regulation "does not apply to operations performed in an area (a) which is wholly or mainly enclosed, and (b) where no uninvolved person is present." Both conditions must be met. A drone flying inside a sealed tank with only the inspection team involved is likely to meet them; a drone flying in a working plant room or warehouse with other staff present does not, whatever the roof overhead.

Older CAA guidance said simply that the drone rules do not apply indoors, and that line still circulates. It predates Article 2A and should not be relied on now. Neither the regulation nor any CAA guidance we found defines "mainly enclosed", so whether a partly open space, such as a ship's hold with its hatches open or an open-topped silo, qualifies is a question to settle with the operator and, where needed, the CAA before the flight.

Where a flight is inside the drone regulation, the usual rules apply: the category of operation, the operator's and pilot's registration, and third-party insurance, which the CAA's Drone Code says is compulsory for flying that is not purely recreational. Health and safety law applies inside or outside the drone regulation: the Confined Spaces Regulations 1997, DSEAR, and the drone as work equipment under the Provision and Use of Work Equipment Regulations 1998.

Only if it is certified for the zone. Where a flammable gas, vapour, mist or dust atmosphere may occur, DSEAR requires the area to be classified into zones, and equipment in each zone must be of the matching category: category 1 in Zone 0 or 20, category 1 or 2 in Zone 1 or 21, and category 1, 2 or 3 in Zone 2 or 22. A drone is equipment. We are not aware of widely available inspection drones certified for use in hazardous zones, so the normal practice is to make the space gas-free, test it, and issue a written permit before the drone goes in.

Two claims are worth checking hard. A drone that carries a gas sensor is not thereby explosion-protected: HSE says of gas detectors that a detector "is not a substitute for safe working practices". And a supplier statement that a drone has been tested in a flammable atmosphere is not the same as certification for a zone. Ask for the certificate, the marking and the exact configuration it covers. What an ATEX marking means is set out in our guide to ATEX and hazardous-area inspection robots.

It is one of the first questions to settle. If nobody enters the space, the emergency arrangements that regulation 5 requires before a person enters do not apply to the flight itself, because nobody is inside to rescue. The drone deployment still needs to fit your site's safe system of work: isolation, gas-free testing where the atmosphere could be hazardous, and the permit your site issues for work at the space.

The catch is recovery. If the drone stalls, loses its link or falls inside, someone may have to go in to fetch it. In our reading of regulation 4(1), which covers entry "for any purpose", that recovery is confined space entry with its own permit, atmosphere testing and rescue arrangements. Decide how a stuck drone would be recovered, by tether, by a hook through the opening, or by a planned entry, before the first flight.

Video, stills and, on many platforms, a 3D point cloud of the interior with each image located on it, so the same spot can be found on the next visit. That is evidence. It is not an NDT result, a certified survey or a structural assessment. Those come from a qualified person applying a method to the evidence: an inspection or integrity engineer for a tank or vessel, a class surveyor for a ship, a structural engineer for a structure.

Two limits matter in practice. Visual imagery shows coating breakdown, cracking, deposits and visible corrosion; it does not measure how much metal is left. Wall thickness needs contact ultrasonic measurement, which some specialist drones can carry, but those give spot readings for an NDT technician to sign off, not a full corrosion map. And lighting, image resolution and stand-off distance decide what can be seen, so agree with the inspector in advance what detail they need to make their call.

BINDT's PCN scheme certifies visual testing as an NDT method at Levels 1, 2 and 3. If the inspection has to count as NDT rather than a first look, ask who holds the relevant certification and whether they will review the imagery.

HSE counts some ships' holds among the confined spaces found in ports, and ballast tanks are confined spaces reached through narrow manholes. The drone questions are the same as for a tank ashore, with one more gatekeeper: the classification society. IACS Recommendation 42, the common guideline for remote inspection techniques, lists drones among them and says the results "are to be acceptable to the attending Surveyor". The inspection plan is to be submitted for acceptance in advance, the surveyor may carry out confirmatory close-up surveys, and if damage is found the surveyor may require close-up survey or thickness measurement without remote techniques.

So on a ship the drone does not decide what is credited: the class society and its surveyor do. Talk to the class society before choosing a supplier, and ask what it requires of the company carrying out the remote inspection. Our guide to ship and vessel inspection robots covers tanks, holds, hull and machinery spaces in more detail.

Drone operators usually quote per job, which makes quotes hard to compare. Asking every operator the same questions makes the differences visible:

Start with one space and one inspection that is already done another way, so the two can be compared. Involve the person who signs the permit and the person who will judge the findings from the first meeting. Agree the measures before anything flies:

Write the exit criteria down too. If the inspector will not accept the evidence, or a recovery needed entry, the pilot stops and says so. That is how we structure a pilot programme. Forge Anvil, the integration software we are developing, is built to talk to as many robots as possible, drones included, and pass what they find into the systems you already run. Which connections a site gets is confirmed in the integration review; the integration patterns are compared in integrating a robot with the software you already run, and the four drone categories are compared on our industrial drones page.