Selecting a pressure transmitter for a hazardous area involves more than picking a certified device. Zone classification, protection concept, approval variant, wetted materials and device configuration all need to match the installation. This guide covers the key selection criteria — and leads directly into the sensor selector for a structured shortlist.
ATEX is the EU legal framework for equipment used in potentially explosive atmospheres (Directive 2014/34/EU). IECEx is an international certification scheme based on IEC standards, recognised in many countries outside the EU including Australia, South Korea and parts of the Middle East. Both are closely related — they reference the same IEC 60079 standard series — but they are not directly interchangeable. The required certificate depends on the country, project specification and device configuration.
For EU installations, ATEX is typically the required approval framework. Some projects may still specify IECEx or additional approvals, especially for international, offshore or company-standardised installations. Always verify which approvals apply to your specific project and installation country.
EU Directive 2014/34/EU. Required for EU installations. Certificate issued by a notified body (e.g. PTB, DEKRA, TÜV). Marked Ex on the nameplate.
International IEC-based certification scheme. Accepted in Australia, Gulf states, South Korea and others. Certificate issued by an ExCB body.
Safety Integrity Level per IEC 61508/61511. Separate from explosion protection — a sensor can be both ATEX-certified and SIL-rated. Verify whether your safety function requires a SIL-assessed device.
North American approvals for hazardous locations. Uses a different classification system (Division 1/2 vs Zone 0/1/2). If your project requires FM or CSA, verify the exact listing in manufacturer documentation.
The zone defines the likelihood and duration of an explosive atmosphere. The required protection level depends on the zone. As a general rule, equipment with a higher protection level may be used in less demanding zones — but the complete marking, certificate conditions, gas group, temperature class and all installation parameters must still match the specific application.
| Zone | Atmosphere | Protection level (EPL) |
|---|---|---|
| Zone 0 | Continuous, long-duration or frequent presence of explosive gas/vapour | EPL Ga — very high protection, e.g. Ex ia |
| Zone 1 | Likely to occur during normal operation | EPL Gb — high protection, e.g. Ex ia/ib, Ex d, Ex e |
| Zone 2 | Not likely during normal operation, only briefly | EPL Gc — normal protection for abnormal conditions |
| Zone 20 | Continuous, long-duration or frequent presence of explosive dust cloud | EPL Da |
| Zone 21 | Dust cloud likely during normal operation | EPL Db |
| Zone 22 | Dust cloud not likely, only briefly | EPL Dc |
Common protection concept markings on pressure transmitters include Ex ia and Ex ib (intrinsic safety), Ex d (flameproof enclosure), Ex e (increased safety) and Ex ec. For 4–20 mA pressure transmitters, intrinsic safety (Ex ia / Ex ib) is the most common concept — the transmitter is typically used with a certified safety barrier or isolator in the safe area, and the complete loop must be verified for Ex ia / Ex ib compliance. Flameproof enclosures (Ex d) contain any ignition rather than preventing it, and allow higher power but result in a heavier device.
| Criterion | What to check |
|---|---|
| Zone & gas group | Zone 0/1/2 for gas, Zone 20/21/22 for dust. Gas group IIA/IIB/IIC — IIC is the most stringent and covers substances such as hydrogen. Note: an IIC marking addresses ignition risk classification; it does not by itself confirm hydrogen compatibility of wetted materials or seals. |
| Temperature class | T1–T6, defining maximum surface temperature. T6 = 85 °C maximum surface temperature. Match to the auto-ignition temperature of the substances present. |
| Protection concept | Ex ia requires a certified barrier; Ex d allows more current but is heavier. Verify the transmitter parameters (Ui, Ii, Pi, Ci, Li) are compatible with your barrier specification. |
| Output signal | 4–20 mA 2-wire is common in ATEX installations and widely used with intrinsic-safety barriers or isolators. HART over 4–20 mA is widely available. Voltage outputs require more care for intrinsic safety compliance. |
| Wetted materials | 316L stainless for general use. Hastelloy C276 for chlorinated or acidic media. Material selection must match the process media — not just the pressure range. |
| Process connection | G1/2 and G1/4 are common for inline installations. Flush diaphragm variants available for viscous or particulate media. NPT for projects with North American piping standards. |
| IP rating | IP65/IP67 are common for outdoor installations depending on exposure. IP68 is relevant for submersible use. IP69K for high-pressure wash-down environments. |
Category 1G equipment is suitable for Zone 0. Category 2G for Zone 1. Category 3G for Zone 2 — provided the full marking, gas group, temperature class and certificate conditions match. A sensor marked Cat. 2G cannot be installed in Zone 0, even if it is otherwise technically similar to a Cat. 1G variant from the same manufacturer.
Most manufacturers offer ATEX as a configuration option — it is not automatically present on the base model. The approval certificate is specific to the device configuration, including housing material, cable entry type and terminal variant. Verify the configuration you specify is covered by the certificate, not just the base series.
For Ex ia installations, the transmitter parameters (Ui, Ii, Pi, Ci, Li) must be compatible with the safety barrier or Zener barrier in the safe area. This is a system requirement — not just a transmitter requirement — and must be addressed before installation.
Pressure range, output signal and certification mark the first filter. Wetted materials, temperature class, protection concept, gas group, IP rating and the approval variant all need to match before a device is suitable for a specific installation.
Verify before specifying: Always confirm the selected device configuration, certification variant, wetted materials, seal material, temperature class and gas group against the official approval certificate and manufacturer specifications. Pressure Selector provides a shortlist for further evaluation — it does not replace engineering review or certification assessment.
For promising matches, use Request Info on any result to prepare a supplier inquiry based on your application requirements, or save sensors to a shortlist for comparison.
Pressure Selector converts application requirements — such as hazardous-area zone classification, pressure range, output signal, process connection, media, wetted materials and approvals — into a structured shortlist of matching pressure sensors.
The results link back to manufacturer specifications and datasheets, so engineers can verify the selected device configuration, approval variant and material compatibility before specifying a device. Coverage includes general industrial transmitters, differential pressure devices, hydrostatic level transmitters and pressure switches from manufacturers including BD Sensors, Yokogawa, Endress+Hauser, Danfoss, BD Sensors, Keller, Wika and others. SIL-assessed variants are available from several manufacturers.