ATEX Equipment Inspections: Grades, Intervals and Records

Key takeaways

• Classification is not the finish line. Zoning the plant discharges one duty; keeping every Ex item fit for its zone is a separate, ongoing duty under workplace directive 1999/92/EC, with its own inspection regime.
• IEC 60079-17 defines three inspection grades: visual, close and detailed. Only a detailed inspection, with the circuit isolated and the enclosure opened, can prove internal condition.
• There are four inspection types: initial (detailed grade, before first use), periodic (interval set by your own assessment, commonly not exceeding 3 years), sample, and continuous supervision by skilled personnel as the alternative to periodic.
• Inspectors need demonstrated competence in the specific protection concepts they inspect, not just an electrical qualification.
• The record lives per Ex item in an equipment register: marking and EPL, grade, date, result, defects and close-out. An inspection you cannot show per item did not happen, in an auditor's eyes.

Two directives, two jobs

ATEX splits the work in two. Directive 2014/34/EU governs the equipment: the manufacturer certifies that the motor, junction box or luminaire meets its category when it leaves the factory. Directive 1999/92/EC (often called ATEX 137) governs the workplace: the employer must keep explosion protection effective in use, which means verified installation and ongoing inspection for the whole life of the installation. It is the same split the EU applies to machines generally under the EU Machinery Regulation 2023/1230: the manufacturer certifies at sale, the user carries the duties in service.

The certificate on the nameplate only describes the day the item was built. Gaskets harden, glands loosen, enclosures corrode, and somebody in year six fits a non-Ex replacement from the shelf. IEC 60079-17 is the standard that turns the employer's duty into a workable regime of grades, types and intervals. If zones and categories are still open questions on your site, start with our guide to hazardous area classification; everything below assumes the classification drawings already exist.

The three inspection grades

Visual

An inspection without tools or access equipment. It finds what a trained eye can see from the ground: obvious damage, corrosion, missing bolts, unauthorised modifications, dust accumulation, and obscured or missing certification labels. It cannot find a loose terminal, a hardened gland seal or a corroded flamepath: those live behind the lid.

Close

Everything the visual grade covers, plus tools and access equipment where needed: steps to reach mounted items, spanners to confirm glands and covers are tight, a check of cable integrity and earth bonding. The enclosure stays shut and the circuit stays live, so no isolation is needed.

Detailed

The enclosure is opened, which in practice means the circuit is isolated first. Only this grade can verify terminal tightness, internal moisture and corrosion, seal condition, correct lamp or element ratings, and the state of flamepath joints on Ex d equipment. It is the most expensive grade and the only one that proves internal condition.

The grades are cumulative: each includes everything below it. A regime built only on visual sweeps therefore misses the defect categories that matter most, glands and internals above all.

Inspection types and how the interval is set

• Initial inspection: detailed grade on every Ex item before first use, and again after any modification or relocation. Installation defects surface here, always more than anyone expects.
• Periodic inspection: the routine regime. The grade and interval come from your own documented assessment: environment, vibration, corrosion, manufacturer guidance and the findings history. The interval between periodic inspections is commonly capped at 3 years; the current edition of IEC 60079-17 and your national adoption of it decide the exact ceiling and the justification required.
• Sample inspection: a defined proportion of items inspected at a higher grade than the routine regime, to test whether the grade and interval are still right. A clean sample supports the current interval; a bad one shortens it or raises the grade.
• Continuous supervision: the alternative to fixed periodic inspections. Skilled personnel who see the equipment frequently during normal work, are trained on the protection concepts present, and record what they find can replace the periodic cycle. It does not replace the initial inspection, and it stands or falls on recording discipline.

The selection logic is simple: harsher environments, more vibration, more corrosion and higher findings rates push toward higher grades and shorter intervals; benign indoor service with a clean history earns the longer end. Whatever comes out of the assessment, the schedule belongs in the same preventive maintenance plan as the rest of the asset base, not in a spreadsheet only the responsible person can find.

Who may inspect

IEC 60079-17 requires inspectors to hold demonstrated, maintained competence: the protection concepts they inspect, the principles of area classification, and the practical skill to judge what they see. The concepts differ enough that competence in one does not transfer: the inspection points on an intrinsically safe loop (barrier parameters, cable segregation, earthing) have almost nothing in common with the flamepath and fastener checks on an Ex d enclosure. Ex personnel certification schemes are the common evidence, but the duty is competence itself, kept current through reassessment. Track who holds which Ex competence, and when it expires, in your maintenance skills matrix: an inspection signed by someone who cannot evidence competence is itself a finding.

The record: one line per Ex item

The backbone of the regime is the equipment register: every Ex item on site, uniquely tagged. Per item, a defensible record holds:

• Tag, location and the zone it sits in.
• Protection type, EPL and full marking string, certificate number.
• The grade and type of the last inspection, the date, and who performed it.
• The result, every defect found, and the work order that closed it out.

This is exactly the shape of work a CMMS holds well. In Fabrico, each Ex item is an asset with its marking and certificate details on file, the visual, close and detailed inspections run as recurring PM tasks with grade-specific checklists, as-found and as-left values are stored per item, a failed checklist line can trigger a follow-up task, and the full history sits behind each asset when the auditor asks. To see the register and inspection cycle set up on your own asset list, book a short demo.

A worked example with real numbers

A food ingredients plant has 342 Ex items: 218 in zone 22 (organic dust in the milling and bagging halls) and 124 in zone 2 (a solvent handling area). The classification drawings were finished last year; nothing had ever been inspected per item.

• Initial detailed inspection, all 342 items, run over six weeks: 41 items with at least one defect, a 12 percent findings rate. The split: 16 cable gland defects (wrong type, missing seals, loose), 9 missing or non-original fasteners, 7 painted-over or missing marking labels, 5 excessive dust accumulations on zone 22 enclosures, 4 non-Ex replacement parts fitted over the years. Three items came out of service on the spot; the rest got work orders.
• Regime set after the initial round: periodic close-grade inspection on a 3-year interval, justified in writing by the dry indoor environment, low vibration and the fact that most initial findings were installation legacy rather than degradation. The 342 items are spread as 114 per year so the workload stays level.
• Layered on top: an annual visual sweep of all 342 items (two technicians, about three days) and an annual detailed-grade sample of 34 items, 10 percent, drawn deliberately from the harshest locations.
• Year one results: the visual sweep raised 11 defects (labels, dust, one cracked lens), the 114 close-grade inspections found 6 more (5 of them glands), and the detailed sample found 2 internal defects (a loose terminal, a hardened gasket). Sample findings rate: 6 percent, which supports the 3-year interval. A sample at 15 or 20 percent would shorten it to 2 years, justification already written.

Total steady-state effort: roughly 150 close- and detailed-grade inspections a year, plus the annual visual sweep, instead of a 342-item panic before every audit.

Common mistakes

• Treating the classification drawings as the finish line. Zoning satisfies the assessment duty. The inspection duty starts where the drawings stop, and it never ends.
• Painting over Ex enclosures. Paint across a flamepath joint on Ex d equipment can invalidate the protection, and a painted-over certification plate makes the item unverifiable, which is itself a defect. Mask Ex items before any repaint.
• Trusting cable glands to the visual grade. Glands are the largest findings category on most sites, and gland tightness and seal condition are invisible from the ground. A regime with no close-grade content never touches them.
• No equipment register. Inspections done per area ("we walked the solvent store in March") cannot prove any individual item was ever inspected. The register, one line per Ex item, is what turns walking around into evidence.
• Defaulting the interval to 3 years with no written justification. The common 3-year figure is a ceiling that your assessment must earn, not an entitlement. Harsh service, vibration or a poor findings rate all argue it down, and an auditor will ask for the reasoning.

Frequently asked questions

How often must ATEX equipment be inspected?

At the interval your own documented assessment sets, based on environment, manufacturer guidance and findings history. For periodic inspections the interval is commonly capped at 3 years, with the applicable edition of IEC 60079-17 and national rules deciding the exact ceiling. Continuous supervision by skilled personnel is the recognised alternative to a fixed cycle.

What are the IEC 60079-17 inspection grades?

Visual (no tools, no access equipment: surface condition, labels, obvious damage), close (tools and access equipment, enclosure stays shut: glands, fasteners, bonding) and detailed (enclosure opened, normally with the circuit isolated: terminals, seals, internal condition, flamepaths). Each grade includes everything the lower grades cover.

Who may inspect Ex equipment?

Personnel with demonstrated, maintained competence in the protection concepts being inspected, plus a working knowledge of area classification. Recognised Ex personnel certification schemes are the usual evidence, but the requirement is competence itself, reassessed regularly and recorded per person.

Do I need to inspect equipment in zone 22?

Yes. Zone 22 carries the same inspection duty as any other zone, and dust service adds its own failure modes: layers that insulate enclosures and raise surface temperatures, and housekeeping that hides labels and damage. Dust zones are where visual sweeps earn their keep between deeper inspections.

What records are required?

An equipment register covering every Ex item, and per item: location and zone, protection type with full marking and EPL, certificate reference, the grade, type, date and inspector of each inspection, the result, and every defect with its close-out. The records must show both that inspections happened and that the chosen grades and intervals are justified.