ATEX is the certification line item that splits a marine panel PC procurement in two. A vessel that never carries flammable cargo can spec a sealed bridge panel PC against marine-grade environmental tests and stop there. A tanker, an LNG carrier, a chemical carrier, an offshore platform, or any vessel with cargo control, fire control, or gas-detection stations inside a classified zone is buying a fundamentally different piece of hardware. The hardware looks similar from the brochure photo. The certificate, the price, the lead time, and the failure mode if you get it wrong do not.
Confusion shows up early. ATEX is the EU directive. IECEx is the international scheme. North American shipyards write Class I, Division 1 or Zone 1 against NEC 505/506. MED Wheel Mark sits on top of all of it for European-flagged vessels. The class society (DNV, ABS, Lloyd’s Register, BV, RINA, ClassNK, RMRS) overlays its own hazardous-area type approval. The naval architect needs every one of those certificates to line up against the vessel’s zoning drawings before a panel PC ever ships. This walk-through covers where hazardous-area compute actually lives on a tanker or offshore platform, what each certification scheme certifies, how to read an Ex marking on a spec sheet, which protection type belongs at each station, and what gets expensive when a procurement team gets ATEX wrong.
Where Does Hazardous-Area Compute Actually Live on a Vessel?
The bridge itself is almost always a safe area. Wheelhouse doors are gas-tight, the space is positive-pressure ventilated, and the surveyor classifies it outside Zone 0, 1, and 2. A standard marine panel PC on the bridge does not need an ATEX certificate. The complication is everything adjacent. On a crude oil tanker, the cargo control room sits next to the bridge but is treated as Zone 2 in many class-society interpretations because hydrocarbon vapor migrates through cable transits during loading and discharge. On an LNG carrier, the gas detection panels, the cargo machinery room, the compressor house, and the area around the manifold are routinely Zone 1. On a chemical tanker, the deck-level pump rooms and the area immediately above the cargo tanks are Zone 1 or Zone 2 depending on cargo class.
Beyond cargo vessels, the same story repeats on offshore production platforms. FPSO and FPU bridges, helideck control stations, and accommodation modules are usually safe areas, but the fire and gas (F&G) panels, the emergency shutdown (ESD) workstations, the cargo metering rooms, and the production control cabins frequently straddle Zone 1 or Zone 2 boundaries. Mobile offshore drilling units (MODUs) layer mud-system zoning on top of hydrocarbon zoning. Naval auxiliaries carrying fuel oils or paint stores have their own classified spaces. The buyer’s job is rarely “spec one ATEX panel PC for the whole vessel” — it is usually “spec different panel PCs for safe-area stations, Zone 2 stations, and the few Zone 1 stations that require certified compute.” A topology choice between a sealed marine panel PC and a separate display plus computer looks different when half the workstations are in a hazardous zone and need to live behind a certified enclosure.
One practical reality drives much of the procurement: an ATEX or IECEx certified panel PC is an order of magnitude more expensive than a sealed marine panel PC. A buyer who broad-brushes “everything on the ship gets an ATEX unit” overspends. A buyer who broad-brushes “the bridge is the only computer that matters” understocks. The right answer is always a zoning drawing review before the spec is written, and the zoning drawing is the authoritative document. The cargo control room may be Zone 2 on a crude carrier and safe area on a product carrier with the same general arrangement. The zoning drawing is what tells procurement which stations need which certificate.
What Do ATEX, IECEx, MED Wheel Mark, and NEC 505 Actually Cover?
ATEX is shorthand for two EU directives. ATEX 2014/34/EU governs equipment intended for use in potentially explosive atmospheres — that is the certificate stamped on the panel PC itself. ATEX 1999/92/EC governs the employer’s obligation to classify and document hazardous areas and protect workers in them — that is what the operator and the shipyard rely on when they zone the vessel. The certificate on the panel PC has to align with the zoning drawing the operator produced under the workplace directive. A vendor’s ATEX certificate states the equipment group, the equipment category, the type of explosive atmosphere (gas or dust), the protection type, the temperature class, and the equipment protection level.
IECEx is the international equivalent administered by the IEC. The underlying technical standards — IEC 60079-0 (general), IEC 60079-1 (flameproof Ex d), IEC 60079-7 (increased safety Ex e), IEC 60079-11 (intrinsic safety Ex i), IEC 60079-2 (pressurized Ex p), IEC 60079-15 (non-incendive Ex n), IEC 60079-31 (dust protection Ex t) — are the same standards ATEX certificates reference. The practical difference is which body issued the certificate and which jurisdiction accepts it. IECEx is accepted on most international flag registers. ATEX is required on European-flagged vessels and at European port calls. Most certified panel PCs from reputable vendors carry both certificates because the test program is shared.
MED Wheel Mark is the certificate the surveyor wants to see on a European-flagged commercial vessel. The Marine Equipment Directive (2014/90/EU) requires that listed safety-critical equipment carry an EU-recognized type approval issued by a notified body, and that certificate carries a wheel-shaped mark. Wheel Mark equipment must also be type-approved by a recognized organization — usually a class society — against the standards the MED references. The wheel mark itself does not replace ATEX; on a SOLAS-class tanker calling at EU ports, the panel PC needs ATEX or IECEx for the hazardous-area certification, MED Wheel Mark plus class-society type approval for the marine carriage certification, and the IEC 60945 environmental test program underneath both. Three certificate stacks live on the same nameplate.
North American shipyards work to a different vocabulary built on the National Electrical Code. NEC 500 is the legacy Class I, Division 1 and Division 2 system that most US offshore platforms and many US-flagged tankers were originally certified to. NEC 505 (gas, Zone 0/1/2) and NEC 506 (dust, Zone 20/21/22) are the newer zone-based articles that map directly to the IEC scheme. A panel PC marked Class I, Zone 1, AEx db IIB T4 Gb under NEC 505 is functionally equivalent to a panel PC marked Ex db IIB T4 Gb under IECEx, but the underlying certification was issued by a Nationally Recognized Testing Laboratory (NRTL) such as UL or FM Approvals, not by a European notified body. A US shipyard reviewing a class society spec sheet built around IECEx markings needs to confirm the NRTL has issued a parallel listing under NEC 505, or the panel PC will be flagged during USCG inspection.
How Do Zone Ratings, Groups, and EPLs Read on a Marine Spec Sheet?
The zone rating is the first piece of an Ex marking and the one the zoning drawing dictates. Zone 0 is a space where an explosive gas atmosphere is present continuously or for long periods. The cargo tank interior on a tanker is Zone 0. No active panel PC belongs there. Zone 1 is a space where an explosive atmosphere is likely to occur in normal operation — open-deck pump rooms, gas-detection cabinets, and many F&G workstations on FPSO modules fall here. Zone 2 is a space where an explosive atmosphere is unlikely in normal operation, and if it occurs, will exist only for a short period — many cargo control rooms, motor rooms adjacent to classified zones, and some bridge wing extensions fall here. Dust zones (20, 21, 22) follow the same logic for grain ships, cement carriers, and biomass terminals.
The gas group is the second piece. Group IIA covers propane-family gases — most general industrial atmospheres. Group IIB covers ethylene, methanol, and most refinery atmospheres. Group IIC covers hydrogen and acetylene — the most reactive gases and the hardest to contain. A panel PC certified for Group IIC is also acceptable for IIB and IIA work; the reverse is not true. A vessel carrying hydrogen, ammonia, or hydrogen-rich gas blends needs IIC-rated equipment in the relevant zones. Many crude oil and product tankers are IIA or IIB depending on cargo. Group I covers underground mining and is irrelevant for marine applications. Group III covers dust atmospheres on grain or cement carriers.
The temperature class is the maximum surface temperature the equipment can reach under fault conditions. T1 is up to 450°C, down to T6 at 85°C. The vessel’s gas data sheet drives the requirement: hydrocarbon vapor with an ignition temperature of 200°C needs T3 or better. T4 (135°C maximum) is the common target for most marine hydrocarbon service. A panel PC with a high-TDP processor running at full load will trip the temperature class faster than a low-power industrial unit, which is why hazardous-area panel PCs lean toward conduction-cooled fanless designs with conservative thermal headroom. Rugged marine environmental tests are the input the Ex test report builds on, not a substitute for it.
The Equipment Protection Level (EPL) closes out the marking. EPLs Ga, Gb, Gc apply to gas atmospheres at Zone 0, Zone 1, and Zone 2 respectively. EPLs Da, Db, Dc apply to dust atmospheres at Zone 20, 21, and 22. A typical hazardous-area marine panel PC marking for a Zone 1 gas application reads something like Ex db IIB T4 Gb — meaning flameproof enclosure (db), Group IIB gases, maximum surface temperature 135°C, suitable for Zone 1. A Zone 2 application can take the same hardware (Gb covers Zone 2) or a less expensive Gc-rated unit if the procurement team is being deliberate about cost.
Which Ex Protection Type Belongs at Each Station?
The protection type is the engineering principle the certificate is built on, and it determines whether the panel PC is buildable for the role at all. Ex d (flameproof, IEC 60079-1) is the workhorse protection type for Zone 1 gas atmospheres. The enclosure is heavy cast aluminum or stainless steel built to contain an internal explosion without transmitting flame to the surrounding atmosphere. Cable entries are certified Ex e or Ex d glands, often with flame paths machined into mating surfaces to several decimal places. Ex d panel PCs are the standard answer for engine room hazardous areas, cargo control on a tanker that crosses Zone 2 into Zone 1, and most F&G workstations on offshore platforms.
Ex e (increased safety, IEC 60079-7) reduces the risk of arcs and high temperatures inside the enclosure through tighter terminal spacing, higher creepage and clearance distances, and conservative thermal design. Ex e is typically used for cable terminations, junction boxes, and motor windings — not standalone panel PCs. A hazardous-area marine panel PC commonly ships in an Ex db enclosure with Ex e terminal compartments. Ex i (intrinsic safety, IEC 60079-11) limits the energy stored or released to a level below what can ignite the explosive atmosphere even under fault conditions. Ex i is the right answer for low-power sensor field devices and small remote display terminals, not for a panel PC running an industrial-class processor with several gigabytes of RAM. Spec writers occasionally try to push Ex i onto a workstation; the maximum allowed energy is well below typical panel PC needs.
Ex p (pressurized, IEC 60079-2) keeps a clean inert or instrument-air purge inside the enclosure so that explosive atmosphere never enters. The panel PC inside the cabinet can be a standard non-Ex unit. Ex p has been the go-to for hazardous-area control cabinets in petrochemical refineries for decades and increasingly shows up on offshore platforms where shoreside engineering culture dominates the spec. The tradeoff is that the purge controller is itself certified equipment, the inert gas or instrument air supply has to be maintained for the life of the cabinet, and a purge fault shuts the cabinet down. On a vessel running on its own utilities, the instrument-air supply often becomes the limiting factor.
Ex n (non-incendive, IEC 60079-15) is the typical protection type for Zone 2 panel PCs. The enclosure is sealed against ingress, the internal components are selected so that no normal-operation arc or hot surface can ignite a Zone 2 atmosphere, and the temperature class is bounded by design. Ex nA, Ex nC, and Ex nR are subtypes. An Ex nA-rated marine panel PC is a meaningfully less expensive answer for a Zone 2 cargo control room than an Ex db unit, and procurement teams should know when Zone 2 zoning allows the substitution. Ex t (IEC 60079-31) covers dust ignition protection by enclosure for Zone 21 and 22 spaces — relevant to bulk grain ships, cement carriers, and biomass berths.
What Is the Procurement Cost of Getting ATEX Wrong?
The most expensive miss is specifying an Ex protection type that does not match the zone. An Ex nA panel PC delivered for a Zone 1 cargo machinery room will be rejected at commissioning, not at the next dry-docking — class surveyors check Ex markings against the zoning drawing during the initial survey of the install. A rejected workstation means the integrator has to source the correct certified unit, often with a 12 to 20 week lead time depending on the manufacturer and the protection type, and the vessel either delays commissioning or operates under a temporary deviation that the flag state may or may not grant. A Zone 1 Ex db panel PC swap on an FPSO topside can run into six figures including engineering hours, rope-access install, and lost production hours during the swap.
The second most expensive miss is overspecifying. A workboat operator who broad-brushes “all bridge and engine room workstations are ATEX Ex db” because someone on the spec team was once burned by an audit finding pays a procurement premium across the entire fleet. On a tug or supply vessel, the bridge is safe area and the engine room is usually safe area too. A standard marine-grade operating-system lifecycle plan on a sealed marine panel PC is the right hardware. ATEX is unnecessary spend, slower delivery, and harder field service. Certified Ex d enclosures cannot be opened in the field without breaking the certificate; the maintenance technician needs the unit ashore for any work that touches the flame path.
The third miss is the certification stack mismatch. A panel PC certified to IECEx Ex db IIB T4 Gb is acceptable on most international flag registers. The same panel PC needs an ATEX certificate to satisfy an EU port call and an NEC 505 listing to satisfy USCG inspection on a US-flagged offshore platform. A vendor selling on price may quote IECEx only; the buyer is responsible for confirming the certificate stack covers every jurisdiction the vessel operates in. Class society type approval is a separate stack. The MED Wheel Mark certificate is a separate stack. The flag-state acceptance is a separate stack. None of them are automatic. Each one needs to be requested as a deliverable with the purchase order, not chased after commissioning.
A useful procurement pattern is to write the spec around the zoning drawing — for each workstation, the spec lists the zone, the gas group, the temperature class, the required EPL, the protection types that are acceptable, and the certificate stack required for the vessel’s flag state and trading pattern. The vendor returns part numbers that match the spec, with the relevant certificates attached. The spec lives in the procurement file alongside the as-built drawings. Three years from now, when a new spec writer is sizing a refit, that file is what tells them which workstations can be replaced like-for-like and which ones need a full re-certification.
Where Should Hazardous-Area Panel PC Spec Work Begin?
Hazardous-area panel PC spec work begins with the vessel’s zoning drawing, not the catalog. The drawing names the zone, the gas group, and the temperature class for every workstation on the ship. The class society’s hazardous-area technical note interprets the drawing against carriage rules. The flag state’s hazardous-area policy says which certificate schemes are accepted. The procurement team translates all three into a part-number-level spec the vendor can quote against. Seatronx’s industrial panel PC lineup includes sealed marine-grade units for safe-area bridges and certified variants qualified for Zone 1 and Zone 2 stations on tankers, LNG carriers, and offshore platforms — the right starting point is a zoning-drawing-driven conversation with applications engineering, not a single SKU pulled from a brochure.
Frequently Asked Questions
Does the bridge of a tanker need ATEX-rated equipment?
Almost never. The bridge enclosure on a tanker is classified as a safe area in the vessel’s zoning drawing because it is gas-tight and ventilated to maintain positive pressure. A standard marine-grade panel PC is the correct hardware for bridge workstations on a crude carrier, product tanker, LNG carrier, or chemical carrier. ATEX equipment is required for cargo control rooms, gas detection panels, and other stations that the zoning drawing places inside Zone 1 or Zone 2, which on most tanker designs sit adjacent to but outside the bridge proper.
What is the difference between ATEX and IECEx?
ATEX is the EU directive (2014/34/EU) that requires equipment used in classified zones inside the European Economic Area to carry a notified-body certificate. IECEx is the international scheme administered by the IEC under the same underlying IEC 60079 technical standards. The test program is functionally the same; the certificate-issuing body and the jurisdictional acceptance differ. Most certified marine panel PCs carry both certificates because the test data overlaps, and the vendor can issue both for the same hardware program.
Can you read an Ex marking without the vendor’s help?
A typical Ex marking such as Ex db IIB T4 Gb decodes as follows: Ex declares the equipment as explosion protected; db is the protection type (flameproof enclosure); IIB is the gas group (covers most hydrocarbon atmospheres); T4 is the temperature class (maximum surface temperature 135°C); Gb is the equipment protection level (suitable for Zone 1 gas atmospheres). A spec writer reading the marking against the zoning drawing can confirm in seconds whether the unit is acceptable. The full certificate also names the issuing body, the standards version, the conditions of use, and the certified configurations.
Is a US-listed NEC 505 panel PC accepted on a non-US flagged vessel?
Acceptance depends on flag-state policy and class society recognition. Most international flag registries accept IECEx certification by default and ATEX by reciprocity. NEC 505 listings are accepted on US-flagged vessels and on some international vessels by class society dispensation, but they are not a default substitute for ATEX or IECEx. On a vessel trading internationally, the safer pattern is to specify IECEx as the baseline and pull in ATEX for European port calls and an NEC 505 listing for USCG inspection, with the same hardware platform certified to all three.
Why is an ATEX panel PC so much more expensive than a marine-grade one?
The certified enclosure carries the most cost. A flameproof Ex db enclosure is a precision casting machined to specific flame-path tolerances on every mating surface, with certified glands at every cable entry. The thermal design also runs more conservatively to hold the temperature class under fault conditions, which limits processor selection. The certification testing itself is expensive: every variant has to be retested against the IEC 60079 standards, and the certificate has to be maintained through periodic surveillance by the issuing body. Lead times for certified variants typically run 12 to 20 weeks against eight weeks or less for a sealed marine-grade unit.
Can a hazardous-area panel PC be field-serviced?
Ex db enclosures cannot be opened in a classified zone without a hot work permit and an active gas-free condition, and even then the flame path mating surfaces have to be inspected and refurbished by a certified technician before the unit can be reclosed. In practice this means a unit needing internal service goes ashore. Ex p pressurized cabinets can be field-serviced more readily because the standard panel PC inside the cabinet is a normal industrial unit, but the purge integrity has to be reestablished and tested before the cabinet is recommissioned. Ex e and Ex i devices have their own field-service constraints documented on the certificate.
Does MED Wheel Mark cover hazardous-area certification on its own?
No. The MED Wheel Mark is the EU’s marine type-approval mark for safety-critical equipment on European-flagged vessels and is functionally equivalent to a class-society type approval for the equipment categories the MED lists. It does not replace ATEX for hazardous-area protection. A workstation in a Zone 1 area on a SOLAS-class tanker calling at EU ports needs ATEX (or IECEx accepted by reciprocity) for the hazardous-area certification and MED Wheel Mark for the marine carriage certification. The two certificates cover different requirements and live on the same nameplate.