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.*