The ingress protection rating IP67 is not an approval for hazardous areas – the two markings concern entirely different risks. Moreover, explosion protection cannot be retrofitted; it is a design decision. For most plants, therefore, the decisive question is not which certified system to procure, but which scope of inspection can be covered outside the zoned areas.
Ingress protection and explosion protection: two different things
This confusion is the most common one in this field and has real consequences in procurement.
Ingress protection protects the device from the environment. It describes dust-tightness and protection against water. It says nothing about whether the device poses an ignition hazard.
Explosion protection protects the environment from the device. It must be ruled out that the device ignites an explosive atmosphere.
An inspection robot brings a whole range of potential ignition sources with it: a battery in the kilowatt-hour range, a dozen electric drives, laser scanners, charging contacts that produce sparks, radio modules, hot surfaces and the possibility of electrostatic charging. Every single one of them must be under control.
Manufacturers' documents state ingress protection ratings prominently because they help sales. On this question they are simply not relevant.
Where Ex zones occur – also outside the process industry
Many regard explosion protection as a chemicals topic. In fact, zoned areas occur in almost all industrial environments – often in small, clearly delimited radii that are easily overlooked on the site plan.
Energy supply. Battery rooms for the auxiliary power supply, in which hydrogen can escape from lead-acid batteries. Areas around transformers with insulating oil. Hydrogen applications in connection with electrolysis and storage.
Water and wastewater. Digestion areas, gas storage and gas utilisation are as a rule designated. The boundary runs within the same plant – the activated sludge area is accessible, the digestion area is not.
Underground infrastructure. Channels and shafts with possible gas ingress, areas where heavy gases accumulate, facilities in the vicinity of gas pipelines.
Process industry. The classic case, with the largest share of zoned area.
In all four cases the same system applies – and the same approach to determining the limits.
How zone classification works
Hazardous areas are classified according to the likelihood with which an explosive atmosphere occurs.
Gases, vapours, mists
| Zone | Occurrence |
|---|---|
| Zone 0 | continuously, for long periods or frequently |
| Zone 1 | occasionally in normal operation |
| Zone 2 | not normally, and if so, only briefly |
Table scrolls sideways.
Dusts
| Zone | Occurrence |
|---|---|
| Zone 20 | continuously, for long periods or frequently |
| Zone 21 | occasionally in normal operation |
| Zone 22 | not normally, and if so, only briefly |
Table scrolls sideways.
The classification is carried out by the operator, not by the device manufacturer. It is recorded in the explosion protection document for the plant.
Two points that are often overlooked:
Zones can change. In certain operating states – filling, emptying, maintenance work – areas may temporarily be classified differently.
Zones are spatially limited. A works is not “an Ex plant”. Zoned areas are mostly clearly delimited radii around defined sources of release.
The legal framework
Explosion protection is governed by two separate strands of regulation, which are often confused.
Equipment side. The ATEX Directive 2014/34/EU governs equipment and protective systems intended for use in hazardous areas. It is addressed to manufacturers and lays down how equipment must be designed and certified.
Operator side. Directive 1999/92/EC governs the protection of workers and is transposed in Germany through the Betriebssicherheitsverordnung (BetrSichV, German Ordinance on Industrial Safety and Health) and the Gefahrstoffverordnung (GefStoffV, German Hazardous Substances Ordinance). It obliges the operator to carry out a workplace risk assessment, to classify zones and to draw up the explosion protection document.
Both are specified in more detail by the Technical Rules for Operational Safety and for Hazardous Substances and by the IEC/EN 60079 series of standards.
In practice this means: the manufacturer supplies a certified device. Whether this device may be used in your specific zone is for you to assess – on the basis of your explosion protection document.
What an Ex approval actually states
An Ex marking is not a blanket clearance. It consists of several items of information, all of which must match the environment.
Equipment category. It determines the zone for which the device is approved. For gases, category 1G corresponds to Zone 0, category 2G to Zone 1 and category 3G to Zone 2. For dusts the corresponding system applies with categories 1D to 3D.
Type of protection. It describes the technical principle by which the ignition hazard is controlled – for example intrinsic safety, pressurisation, flameproof enclosure or encapsulation. In complex devices, several principles are combined.
Gas group. It assigns the device to the properties of the substances present. Group IIA includes, for example, propane, group IIB ethylene, group IIC among others hydrogen and acetylene. IIC imposes the highest requirements.
Temperature class. It limits the maximum surface temperature of the device. This must be below the ignition temperature of the substance present; the classes range from T1 to T6.
Of practical consequence: a device certified for Zone 1 in gas group IIB must not be used in an area with a hydrogen atmosphere – there, IIC is required. Given the growth in hydrogen applications, this is a question to check that is becoming increasingly relevant.
An Ex approval is therefore always a statement about a combination: zone, gas group and temperature class. All three must match the plant. A statement “Ex: yes” would be misleading.
Why explosion protection cannot be retrofitted
This question is asked regularly, and the answer is clear: it cannot be done.
Ignition protection is not an accessory but a design principle that runs through the entire device.
The battery must be enclosed or made intrinsically safe in such a way that neither sparks nor hot surfaces nor escaping gases can cause ignition. With energy contents in the kilowatt-hour range, this is a considerable design requirement.
The drives are moving electrical components that generate heat. Enclosing them changes weight, volume and heat dissipation – and with them the entire mechanics.
Charging is a problem of its own. Charging contacts produce sparks when disconnected. Charging in zoned areas therefore requires special solutions or takes place outside the zone.
Sensors and radio must also be included in the protection concept.
In addition: for category 2G equipment, the involvement of a notified body in the conformity assessment procedure is mandatory. A self-declaration is ruled out.
A standard robot enclosed after the fact is therefore not an Ex device, but a standard robot with an additional housing. It must not be used in zoned areas.
On the range of certified systems
The design effort explains the market structure: for only very few mobile inspection robots do the manufacturers state a Zone 1 approval under ATEX and IECEx – for ground-based tracked systems as well as for at least one legged system. They are exceptions and are priced considerably above standard systems.
The differences between them concern above all mobility: tracked vehicles are robust and carry high payloads, but depend on largely level terrain. A legged system also opens up stairs and multiple levels – which can be decisive in multi-storey process plants.
We maintain model-specific information on certification status in the robot database, each with source and date of check.
The realistic approach: delimiting the zones
For most operators, the sensible first step is not to procure a certified system, but to determine precisely what lies outside the zones.
Typically not zoned are:
- pipe racks and routes outside the release radii
- energy centres, boiler houses, transformer stations
- cooling water circuits and cooling towers
- storage areas for non-flammable substances
- site roads, traffic areas, loading areas
- the edges of tank farms
- workshops and ancillary facilities
- in wastewater treatment plants: the entire activated sludge area outside the digestion zone
Added to this is a technique that is often overlooked: capture from a distance. Many inspection tasks – thermographic checks, reading of gauges, visual inspection – can be carried out with sufficient optical zoom from the edge of a zone, without the device entering it.
Approach:
- Consult the explosion protection document and mark the zoned areas on the site plan
- Sort today's scope of inspection accordingly: inside, outside, visible from outside
- Assess which share can be covered by a standard system
- Only consider a certified system once a substantial, economically relevant scope of inspection necessarily lies inside the zone
Experience shows that the share lying outside is larger than initially assumed.
Gas detection is not an Ex approval
A misunderstanding that persists – also in manufacturers' documents.
An inspection robot can be equipped with multi-gas sensors and measure concentrations of carbon monoxide, hydrogen sulphide, oxygen or flammable gases. This is a useful function, for example for reconnaissance before an area is entered or for condition monitoring outside the zones.
The ability to detect gas does not, however, entitle the device to be operated in an Ex zone. Technically and legally, the two have nothing to do with each other.
Watch out for this mixing of the two in product descriptions. Wording such as “suitable for chemical plants” in connection with gas sensors is not evidence of an approval. The only reliable wording is gas detection in non-hazardous areas.
Before procurement
- Explosion protection document for the plant is available and up to date
- Zoned areas marked on the site plan
- Scope of inspection sorted into inside / outside / visible from outside
- Where use in a zone is planned: zone, gas group and temperature class of the plant determined
- Ex marking of the device checked in full, not only the zone information
- EU-type examination certificate available, notified body verified via NANDO
- Charging concept clarified – inside or outside the zone
- Written statement from the manufacturer requested: permissible payloads, lever arms and load cases – and whether retrofits are part of the certified Ex concept
- Occupational safety specialist and explosion protection officer involved early
This checklist will be offered as a download once the template exists.
The second-to-last point is important: sensors fitted afterwards can invalidate the Ex approval of the system as a whole if they are not part of the certified concept.
Sources
- Directive 2014/34/EU on the harmonisation of the laws of the Member States relating to equipment and protective systems intended for use in potentially explosive atmospheres European Union accessed 15 August 2026
- Directive 1999/92/EC on minimum requirements for improving the safety and health protection of workers potentially at risk from explosive atmospheres European Union accessed 15 August 2026
- Gefahrstoffverordnung Bundesministerium der Justiz accessed 15 August 2026
- Betriebssicherheitsverordnung Bundesministerium der Justiz accessed 15 August 2026
- Technische Regeln für Betriebssicherheit und für Gefahrstoffe Bundesanstalt für Arbeitsschutz und Arbeitsmedizin accessed 15 August 2026
- NANDO – database of notified bodies European Commission accessed 15 August 2026
Change log (2)
- 5 October 2026 Initial publication First publication of the English version.
- 5 October 2026 Update “Before procurement” checklist made more specific – written statement from the manufacturer on payloads, lever arms, load cases and retrofits.