A client points at equipment and asks: "Is this ATEX?" A question that doesn't yield an answer. ATEX isn't a property of the equipment — it's a certificate that says where the equipment may be installed. Petrochemical equipment certified for Zone 2 in oil vapours is illegal in Zone 1 for acetylene — and conversely, expensive Zone 0 equipment from a refinery would never be needed in a wheat silo, even though dust explosions do happen there.
This article is a decision framework for three pieces: how to correctly categorise the space (zone), what equipment belongs there (category + protection method), and where ATEX legislation meets the real cost of certified personnel.
Two directives people confuse
ATEX = Atmosphères Explosibles = explosive atmospheres. Two EU directives:
- ATEX 114 (Directive 2014/34/EU) — equipment. It defines how equipment is certified, manufactured and placed on the market. It applies to the manufacturer / importer.
- ATEX 153 (Directive 1999/92/EC) — workplace. It defines how the employer identifies explosive zones, classifies them, documents them (Explosion Protection Document — EPD), and what equipment may be used there.
The client pays for the first (buys the products), is responsible for the second (must have an EPD under NV č. 393/2006 Z.z.). It is checked by the Labour Inspectorate + (for some industries) the Chief Mining Authority, not the trade inspectorate.
Zones — two worlds, six categories
Gas / vapour (G — Gas)
- Zone 0 — explosive atmosphere is present continuously or for long periods (> 1000 h/year). Inside a reactor, inside a closed tank with a volatile medium, the headspace above petrol in a tank.
- Zone 1 — explosive atmosphere is likely to occur in normal operation (10–1000 h/year). Around valves, filling points, pumps, sampling points.
- Zone 2 — explosive atmosphere is unlikely in normal operation; if it does occur, it's short (< 10 h/year). Inside a compressor station building, a ventilated hall with gas equipment.
Dust (D — Dust)
- Zone 20 — explosive dust cloud continuously / for long periods. Inside a silo, inside a filter housing, inside a pneumatic conveyor.
- Zone 21 — explosive dust cloud likely in normal operation. Filling points, emptying points, cleaning points.
- Zone 22 — explosive dust cloud unlikely; if it occurs, it's short. Around dusty equipment, floors in a flour warehouse.
Equipment — category + group
- Group I — mining equipment (coal mines), categories M1 (very high safety, may remain on when an explosive mixture appears) and M2 (switches off on detection).
- Group II — surface industries. Categories:
- - 1G for Zone 0, 1D for Zone 20 (very high safety, 2 protection methods)
- - 2G for Zone 1, 2D for Zone 21 (high safety, 1 method + independent monitoring)
- - 3G for Zone 2, 3D for Zone 22 (normal safety, 1 method)
Investor's rule: equipment of a higher category may go into a lower zone (1G may go into Zone 1 and Zone 2). The reverse is NOT allowed. Buying 1G equipment preventively "just in case" costs 3–5× more than 3G — unnecessarily, if the space is in fact Zone 2.
Protection methods under EN 60079-x
The ATEX certificate defines by what method the equipment is protected against explosion. The most common:
- Ex d (flameproof, EN 60079-1) — a massive enclosure withstands an explosion inside it, flames don't escape. Motors, switchgear, luminaires. Heavy, expensive, but universal for 2G/3G.
- Ex i (intrinsic safety, EN 60079-11) — the circuit never has enough energy to ignite. Sensors, transmitters, HMI panels with signal < 250 mV / < 100 mA. The safest for Zone 0/1 (1G/2G).
- Ex e (increased safety, EN 60079-7) — fault-free design without sparks. Terminal blocks, brushless motors.
- Ex p (pressurised, EN 60079-2) — internal overpressure of an inert gas prevents the explosive atmosphere from entering. Analysers in Zone 1, server racks in a Zone 2 hall.
- Ex t (dust protection, EN 60079-31) — tight enclosure, IP6x, for dust Zones 20/21/22.
- Ex n (Zone 2 only, EN 60079-15) — the simplest protection for 3G. Standard industrial equipment with minor modifications (no-spark switches, sealed switches).
When intrinsic safety (Ex i) beats flameproof (Ex d)
The most common mistake: the investor buys an Ex d sensor for €800 because "it's safer," when an Ex i sensor for €280 would do. Ex d is suitable for high-current (motor, heater, switch with a real current load). Ex i is suitable for low-current (signal, measurement, control).
Decision criterion:
- Circuit energy < 1.3 W and max current < 100 mA? → Ex i is the right choice. Cheaper, easier to install (standard cabling, no need for Ex d enclosures or Ex d cable glands).
- Circuit energy > 5 W or high-current? → Ex d or Ex e.
Example from Slovnaft (Vlčie hrdlo refinery): Zone 1 at the loading rack. Pressure sensor: 4–20 mA, 24 V supply, 20 mA current, energy 0.48 W → Ex ia (intrinsic safety, the highest level for Zone 0/1). Price €350 vs. an Ex d alternative for €1,200. Installation: into the same Ex i barrier cabinet with 16 channels for €4,800 — vs. 16× Ex d cable glands and flameproof conduits for €15–20k.
Real-world examples from three sectors
Slovnaft Vlčie hrdlo (petrochemistry)
Zone classification under the internal EPD (revised every 3 years): - Zone 0: inside reactors, inside tanks with petrol / diesel, inside pipelines above the boiling point - Zone 1: around valves, tanker filling points, pumping stations, sampling points - Zone 2: the rest of the outdoor production area, compressor stations, pressurised control buildings
Typical equipment in Zone 1: Endress+Hauser Cerabar PMC51 pressure transmitters (Ex ia, ~€650), Krohne Optimass flowmeters (Ex d, ~€4,200), Auma SAR motorised valves (Ex d, ~€6,800). Luminaires in Zone 1: Cooper Crouse-Hinds GHG 510 (Ex d, ~€420 vs. €60 non-Ex).
Slovalco (aluminium smelter, dusty environment)
Aluminium dust is explosive — the lower explosive limit (LEL) is 35 g/m³, with ignition energy < 50 mJ. Classification: - Zone 20: inside electrolysers, inside extraction filter housings - Zone 21: anode loading stations, cathode replacement points, dust conveyor belts - Zone 22: the rest of the production hall with aluminium dust accumulation
Typical equipment: dust-tight IE3 Ex tb motors (IP6X, ~30% more expensive than standard IE3), Beckhoff CP6603 HMI panels in Ex e protection, Wolf ATEX LED W-71 luminaires (Ex tb for Zone 21/22).
Grain elevator (agricultural silo)
Flour / grain dust has LEL ~50 g/m³, MIE (minimum ignition energy) 30–100 mJ. Classification: - Zone 20: inside the silo, inside pneumatic conveyors - Zone 21: filling valves, discharge points, levelling equipment - Zone 22: outer perimeter areas of the silo
This is where the risk is most often underestimated. Real incidents (DeBruce Grain Elevator, Kansas, 1998 — 7 deaths, grain dust explosion) still happen. The Slovak Republic has NV č. 393/2006 and STN EN 60079-10-2 as binding — but in 30% of smaller agricultural cooperatives the EPD was never produced.
What it costs — real EUR
Certified personnel
- ATEX appointed person (internal / external expert) — responsible for EPD review. External audit: €1,500–3,500 for a site up to 5,000 m².
- Inspection technician for designated equipment (E2A in Ex environment) — STN 33 1500, authorisation from TI SR. Hourly rate €60–120, annual pre-installation inspection €800–2,500 depending on scope.
- EPSI (Ex installer authorised under § 22 of Vyhláška 508/2009 Z. z.) — installation and repair of Ex equipment. Hourly rate €50–90.
- Notified body for ATEX 114 audit (if you manufacture Ex equipment, not just use it) — TÜV SÜD, FTZÚ Ostrava, INERIS, IBExU. Quality Assurance Notification (QAN) audit under Module D: €8–18k annually.
EPD documentation (Explosion Protection Document)
A client without an EPD during a Labour Inspectorate check gets a fine of €330–33,000 (NV č. 393/2006 + Act 124/2006 Z.z. on OHS). External consultant work:
- Small operating unit (1 hall, < 1,000 m²) — €1,800–3,200
- Mid-size site (5,000–20,000 m², several buildings) — €6,000–15,000
- Large industrial site (refinery, aluminium smelter, cement plant) — €25,000–80,000
The EPD contains: identification of explosive atmosphere sources, zone classification (with floor plans), an equipment list with categories, organisational measures, technical measures, an inspection plan.
Installed value of Ex equipment
As a guideline (what the client pays for equipment, not installation):
- Zone 2 area — increase of ~30–50% over non-Ex
- Zone 1 area — increase of ~80–150%
- Zone 0 area (rare, inside tanks) — increase of 200–400%
For a project with a €500k equipment budget in Zone 1 (typical extruder + filling line in chemistry) the ATEX uplift runs €400–750k. This is the line item most often omitted from preliminary calculations.
What clients most often get wrong
- 1.Assume Zone 2 without an EPD. "It's a ventilated hall, it's probably Zone 2" — without calculation, without a consultant, without an EPD. On the first Labour Inspectorate visit they get a fine and the entire production is shut down.
- 2.Buy Ex d when Ex i would do. Because "it's safer" — without knowing that intrinsic safety is the technically more robust method for low-current measurement than flameproof.
- 3.Mix Ex i and non-Ex circuits. Without an Ex i barrier (Pepperl+Fuchs KFD2, MTL 7700) in the same cabinet. The Ex i signal gets "contaminated" by non-Ex current and loses certification.
- 4.Install a certified HMI panel via a non-Ex cable gland. The equipment's certificate is voided. An Ex d enclosure with an Ex e gland is not Ex d as a whole.
- 5.Replace an Ex motor after a failure with a standard IE3. "It looked the same." The line runs for 6 months until the inspectorate finds out — a fine plus forced replacement plus incident documentation.
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*We do ATEX zone audits and EPD documentation for production sites in SR/CZ/AT. The first consultation (45 min) walks through your site's current zone classification and flags the places where documentation is most often missing or equipment is incorrectly categorised.*