Explosion-Proof Card Readers: Ex Zones, Markings and Selection

Specify a hazardous-area card reader from the classification of its mounting point and verified conformity documents for the exact equipment. An Ex marking describes claimed protection; it does not by itself prove certification or approve a connected installation. In particular, our current TP-110 records contain supplier-reported markings but no verified ATEX or IECEx certificate.

This guide helps purchasers prepare a specification and document review. The site’s competent hazardous-area designer determines the equipment, circuits and installation requirements under the applicable national rules and standards.

Start with the zone and substances

Obtain the classification drawing for the reader, lock, junction box and cable route. A facility name such as “refinery” does not classify every gate or room. Gas and dust zones describe different atmospheres, and approval for one does not establish approval for the other.

The usual zone-to-EPL relationship and EU category selection are summarized below. The EU workplace rules also require suitability for the atmosphere and the site’s explosion-protection assessment; the table is not an installation approval.

Location	Atmosphere occurrence	Usual acceptable EPLs	EU equipment categories for that atmosphere
Gas Zone 0	Continuous, frequent or prolonged	Ga	1G
Gas Zone 1	Occasional during normal operation	Ga or Gb	1G or 2G
Gas Zone 2	Unlikely during normal operation; brief if present	Ga, Gb or Gc	1G, 2G or 3G
Dust Zone 20	Continuous, frequent or prolonged dust cloud	Da	1D
Dust Zone 21	Occasional dust cloud during normal operation	Da or Db	1D or 2D
Dust Zone 22	Unlikely dust cloud during normal operation; brief if present	Da, Db or Dc	1D, 2D or 3D

A higher EPL can satisfy the level requirement in a less demanding zone, subject to the other selection conditions. It does not automatically satisfy gas or dust group, temperature, environment or local acceptance. Underground mining equipment is outside this guide’s scope.

For US installations, check the accepted Class/Division or Zone approval and installation requirements. An ATEX or IECEx document alone does not demonstrate compliance with OSHA’s hazardous-location requirements.

Read the complete marking

The following is an illustrative gas marking, not a statement that a catalog product has been certified: II 1G Ex ia IIC T4 Ga.

Element	What to verify
II 1G	ATEX surface-industry equipment group, category and gas designation
Ex ia	Intrinsic-safety protection concept and level; confirm the cited standard and scope
IIC	Gas subgroup; match it to the actual substances and any certificate restrictions
T4	Gas temperature class: maximum surface temperature 135 °C under specified conditions
Ga	Gas EPL; check it against the site’s requirement
Ta or Tamb	Approved ambient range, read with the certificate and instructions
Certificate X suffix	Specific Conditions of Use must be reviewed and implemented
Certificate U suffix	Component certification with limitations; not a complete equipment approval

Gas subgroups IIA, IIB and IIC are separate from dust subgroups IIIA, IIIB and IIIC. Group selection follows the relevant hierarchy, but a gas-group marking does not supply dust approval. For a combined gas-and-dust installation, review both markings and the respective conditions.

Gas temperature classes describe surface-temperature limits, not the outdoor temperature at which the reader will work:

Gas class	Maximum surface temperature
T1	450 °C
T2	300 °C
T3	200 °C
T4	135 °C
T5	100 °C
T6	85 °C

Dust selection needs the tested dust-cloud and dust-layer ignition properties, anticipated accumulation and the equipment’s documented temperature conditions. Do not substitute a gas T-class or interpret a layer-qualified dust marking from plain text alone. The required margins and any thicker-layer assessment belong in the site’s design review.

Obtain the approved ambient range explicitly. A general operating-temperature specification is not a certified Ex range, and missing marking information should not be filled with an assumed default. Cleaning, electrostatic charging, impact, corrosion and accessory conditions can also limit use.

Compare Ex i, Ex d and Ex e

Intrinsic safety, Ex i, controls electrical and thermal ignition energy in the assessed circuit. Levels ia, ib and ic use different fault-assessment requirements and generally correspond to Ga/Da, Gb/Db and Gc/Dc respectively. The overall equipment and system marking governs; an intrinsically safe subcircuit does not raise the protection level of an entire assembly.

Flameproof protection, Ex d, contains an internal explosion and prevents transmission through its designed enclosure and flame paths. The familiar db level corresponds to Gb. The d family also has other levels, so avoid treating the broad term “Ex d” as a universal zone rating. Entries, windows and enclosure construction must remain within the approved design.

Increased safety, Ex e, addresses equipment without unprotected ignition-producing arcs or sparks under the assessed conditions. The eb and ec levels differ. It often appears with another protection concept in an assembly; an Ex terminal compartment does not alone approve the reader electronics connected to it.

Protection family	Procurement focus	Connection review
Ex i, IEC 60079-11	Complete marking, protected circuits and required system assessment	Associated apparatus, circuit parameters, cables and any permitted system configuration
Ex d, IEC 60079-1	Actual protection level, enclosure and permitted entries	Approved entry arrangement, cables, plugs and manufacturer instructions
Ex e, IEC 60079-7	Actual protection level and scope of protected equipment	Termination, entry and assembly requirements in the approved design

Encapsulation Ex m and dust enclosure protection Ex t are additional concepts. Potting or an IP label alone does not establish either. These distinctions follow the IECEx protection-technique overview; check the current standards and the equipment’s own documents for the project.

Request the right conformity documents

For an ATEX electrical reader, request the EU Declaration of Conformity, instructions and evidence of the applicable conformity-assessment route. Category 1 and category 2 electrical equipment normally use EU-type examination with the applicable production procedure; unit verification is an alternative route. Category 3 can use internal production control. Category 2 non-electrical equipment follows a different route, so “every category 1 or 2 item needs the same certificate” is inaccurate.

The notified-body number follows the CE mark when that body participates in production control. A type-examination body’s involvement alone does not establish which number belongs there. Check the route and issuing body instead of applying a blanket rule to all categories. The ATEX Directive and European Commission guidance explain these distinctions.

For IECEx, check the current online Certificate of Conformity, its exact equipment description, issue, status, annexes and linked report references. A downloaded copy may have been superseded. A U component certificate is not a stand-alone approval for a finished reader; X identifies conditions requiring attention. See the IECEx certificate guidance.

Document review should answer:

• Does the approval cover the exact model, keypad option and hardware configuration?
• Do gas/dust scope, EPL, temperatures and ambient limits match the site?
• Are the instructions, schedules and Specific Conditions of Use available?
• Is the claimed IECEx certificate current in the online system?
• Are the circuit parameters and installation documentation sufficient for the proposed connections?

Review the connected circuit and installation

A common arrangement places ordinary controllers and supplies in an unclassified area, reducing equipment inside the zone. This is a design choice, not a universal requirement that every controller or barrier be outside. Equipment installed inside needs suitable protection and approval for that location. Square-bracket associated-apparatus markings describe protected connected circuits; review the apparatus’s own location suitability separately.

For an entity-based IS loop, obtain reader input parameters such as Ui, Ii, Pi, Ci and Li and the associated apparatus’s output and permitted external-circuit values. The designer checks them with cable capacitance and inductance and any permitted combined L/C pairs. Multiple sources or a different system concept require the relevant assessment rather than a generic calculator. IEC 60079-25 covers intrinsically safe systems; installation requirements are addressed in IEC 60079-14.

Account for power, data, control lines and accessories in the approved circuit arrangement. A product statement that no external barrier is needed is insufficient without the supporting design documents. Functional Wiegand or RS485 communication through an interface must also be checked; a successful bench test does not prove explosion protection. Our reader-interface guide covers the functional interface differences.

Zener barriers commonly depend on a high-integrity IS earth. Galvanic isolation can avoid that particular dependence, but does not remove every protective bonding, shielding or functional-earthing requirement. Follow the selected apparatus instructions and site design. Do not turn a general earth-resistance figure or terminal-separation distance into a universal installation rule.

The same discipline applies to cable entries, unused openings, segregation and bonding: use the selected protection concept, applicable installation standard and manufacturer instructions. Live work is not authorized merely because a circuit is intrinsically safe. Maintenance and isolation procedures require their own competent assessment.

Locks, exit devices and door contacts need evaluation too. Some simple passive devices may be accepted as simple apparatus in an assessed IS system; powered or illuminated assemblies must not be assumed to qualify. Confirm release behavior and emergency egress independently of credential-reading success.

TP-110: current evidence and ordering status

TP-110’s supplier documentation reports gas marking Ex ia IIC T6 Ga and a dust marking, along with LF/HF reading and Wiegand 34/66 or RS485 output. We have no verified ATEX or IECEx certificate, certified system drawing or entity-parameter set in the current project records. We therefore cannot substantiate a specific zone installation or the supplier’s barrier-free claim.

Treat TP-110 as a document-review candidate, not a verified hazardous-area recommendation. If procurement requires certified Ex equipment, leave the selection open until acceptable evidence is received and reviewed. The tamper-proof reader category also includes ordinary security readers, which must not inherit Ex suitability from their category placement.

RFQ checklist and next steps

• Classification for each mounting point and the required approval scheme
• Actual gas/dust groups, ignition data and required EPL/category
• Ambient and environmental conditions, including cleaning and dust accumulation
• Exact equipment configuration and complete conformity documents
• Approved circuit/interface arrangement and cable requirements
• Credential sample, required data and controller input format
• Evaluation of locks, exit devices, contacts and accessories
• Competent design, installation and initial-inspection responsibilities

Send these requirements through the RFQ form. We can review catalog interfaces and the documents available for a candidate, identify missing evidence and arrange safe-area bench samples. Classified-area approval and final circuit selection remain with the project’s qualified review.

Sources

Technical and regulatory review date: October 1, 2026. This page summarizes procurement checks; it is not a substitute for the applicable standards or an equipment certificate.

• EU workplace Directive 1999/92/EC, Annexes I and II
• IECEx 2024 installation and equipment-selection presentation
• IEC 60079-11:2023, intrinsic safety scope
• IECEx online certificate-system instructions
• HSA intrinsic-safety instrumentation guidance, earthing discussion