Fixed Gas Detectors for Hazardous Areas: What Really Matters Before You Choose

Installation, maintenance, and long-term reliability: a technical guide for engineers and professionals selecting an industrial fixed gas detector for real-world applications

When selecting a fixed gas detector for a hazardous area, compliance certifications alone are not enough. An ATEX marking is a mandatory requirement, but it does not tell you how the detector will perform during installation, after years of continuous operation, or when the sensing element eventually needs to be replaced.

The most relevant question is not "Is this detector certified?" but rather "How will it perform throughout the entire lifecycle of the plant?" Installation, system integration, functional reliability, maintenance requirements, and total cost of ownership are the factors that determine whether an industrial ATEX gas detector truly delivers on its promises.

In this guide, we'll examine the key criteria to consider before choosing a fixed gas detector for hazardous areas: ATEX and IECEx certifications, SIL functional safety, certified performance, installation flexibility, system integration, maintenance requirements, and total lifecycle costs.

ATEX Certification for Zone 1: The Starting Point, Not the Finish Line

In hazardous areas, ATEX certification is not a competitive advantage—it's the minimum requirement for installing a fixed gas detector safely and in compliance with applicable regulations.

The European ATEX Directive (2014/34/EU) applies to equipment intended for use in potentially explosive atmospheres and defines the conditions under which devices can safely operate in the presence of flammable gases, vapours, mists, or combustible dusts.

The hazardous area classification determines the required level of protection. Zone 1 is considered a high-risk environment where an explosive atmosphere is likely to occur during normal operation—not only under abnormal or accidental conditions, but as part of the plant's routine process. A detector certified for Zone 1 must therefore be specifically designed to operate reliably and continuously under these demanding conditions.

For plant designers, system integrators, and installation contractors, verifying the correct ATEX marking is always the first step.

However, stopping at certification alone would be a mistake.

An industrial ATEX gas detector may fully comply with the requirements for its installation area while still proving difficult to wire, challenging to integrate with existing control systems, or unnecessarily complex to maintain. Certification tells you where a detector can be installed—not how practical, efficient, or cost-effective it will be throughout its service life.

Why IECEx Certification Also Matters

Alongside ATEX, it is worth considering IECEx certification, the internationally recognised certification scheme for equipment used in explosive atmospheres.

When a detector carries both ATEX and IECEx certifications—as is the case with the Tecnocontrol GDS850—it has been independently assessed for both the European market and countries that adopt the IECEx scheme. This is particularly valuable for international projects, multinational EPC contractors, or facilities operating under global procurement specifications and audit requirements.

Functional Safety: What SIL Really Means for an Industrial Gas Detector

In industrial gas detection, the term SIL is often used as a generic synonym for "higher safety." In reality, it has a much more specific technical meaning.

SIL (Safety Integrity Level) defines the integrity of a safety function. Simply put, it measures the probability that a safety system will perform its intended function correctly whenever required.

For a fixed gas detector, the question is straightforward:

What is the probability that the detector will fail to trigger an alarm when hazardous gas is actually present?

SIL is therefore a quantitative measure of the probability of dangerous failure on demand. The higher the SIL level, the lower the probability that the safety function will fail when needed.

This shifts the focus away from the individual detector and towards the overall safety architecture.

A gas detector may carry a specific SIL rating, but the actual functional safety of the installation also depends on factors such as detector placement, signal management, control logic, and system redundancy.

Because of technological limitations, an individual gas detector cannot achieve a hardware certification beyond SIL 2. This means the device has been designed and independently verified to maintain its dangerous failure probability within the limits defined for SIL 2.

If the detector is also certified to SIL 3 at software level—as is the case with the Tecnocontrol GDS850—it means that the firmware architecture has been developed according to more stringent functional safety requirements, supporting applications that demand a higher overall integrity level.

However, one important clarification is necessary.

A single gas detector, considered on its own, cannot provide a complete gas detection safety function beyond SIL 2.

Two SIL 2-certified GDS850 detectors installed on the same critical detection point and correctly integrated into the plant's safety system can form a redundant architecture in which the failure of one detector does not compromise the overall safety function.

In this way, the detection point can contribute to achieving a higher functional safety target—up to a configuration comparable with SIL 3, depending on the overall system design.

This is not an inherent property of the detector itself. It is the result of careful engineering, functional safety analysis, and validation of the complete safety architecture.

For engineering firms, system designers, and maintenance professionals, this distinction is essential.

SIL should never be treated as a simple number for comparing products. Instead, it should be viewed as a design criterion that helps determine the level of reliability required by the risk assessment and guides the development of a gas detection system capable of maintaining its safety function throughout the plant's operational life.

Installation in the Field: Why Wiring Flexibility Matters

Anyone who installs fixed gas detectors in hazardous areas knows that real-world conditions rarely match the drawings.

Cable routes approach from different directions, installation space is often limited, and detector orientation may be dictated by both sensor positioning and the behaviour of the target gas.

In this context, the mechanical and electrical flexibility of an ATEX-certified industrial gas detector is far more than a convenience—it directly affects installation time, commissioning efficiency, and the overall quality of the finished system.

One specification that is frequently overlooked during product selection is the number and arrangement of cable entries.

A detector with only one cable entry forces installers to route all wiring through a single point, making cable management more complicated, limiting circuit separation, and increasing the complexity of future maintenance activities.

Four cable entries—as provided on the Tecnocontrol GDS850—allow connections to be arranged according to the actual installation layout, reducing unnecessary constraints and simplifying future service interventions.

Mounting flexibility is equally important.

A detector that can be installed in multiple orientations, adapting to cable routing requirements while maintaining easy maintenance access, reduces the compromises that often occur during installation and later complicate servicing.

These are not secondary considerations.

In hazardous areas, every intervention—from initial installation to sensor replacement—must comply with strict regulatory requirements. The more a detector has been engineered for practical field maintenance, the lower the risk of installation errors, unexpected complications, and regulatory non-compliance.

System Integration: Modbus, Relay Outputs and Safety Logic

A fixed gas detector never operates in isolation.

It forms part of a wider safety architecture that typically includes gas control panels, PLCs, SCADA systems, and emergency shutdown logic. The quality of the detector's integration determines whether the entire system operates as a cohesive safety solution rather than simply a collection of independent devices.

When selecting an ATEX gas detector, the first point to verify is compatibility with the existing control infrastructure.

The 4–20 mA analogue output remains the industry standard for connection to gas control panels and interface modules. It continuously transmits the measured gas concentration and is compatible with virtually every industrial monitoring system.

Alongside the analogue output, Modbus RS485 provides direct digital communication with gas controllers and SCADA systems.

Unlike a simple analogue signal, Modbus transmits not only gas concentration but also diagnostic information and device status, enabling operators to monitor detector health remotely and improve predictive maintenance.

For facilities with centralised supervision, this capability offers significant operational advantages.

Relay outputs deserve equal attention.

Standard relays are suitable for many applications, but where the gas detection system forms part of a functional safety architecture, relay outputs may also need to comply with SIL requirements.

The Tecnocontrol GDS850, for example, is available with either standard relays or SIL-certified safety relays, allowing the detector to match the required integrity level without relying on additional external components.

Another specification that is often overlooked is fault signal management.

A detector capable of clearly distinguishing between alarm conditions and device faults—and communicating both reliably to the control system—allows operators to diagnose events more accurately while reducing unnecessary maintenance interventions and false assumptions.

In hazardous environments, this distinction has direct operational consequences.

Certified Performance: Why Technical Specifications Alone Are Not Enough

Technical datasheets are essential when evaluating an industrial ATEX gas detector.

However, not all technical specifications carry the same weight.

Manufacturers can state response times, alarm thresholds, or measurement accuracy.

Demonstrating that these values have been independently verified according to internationally recognised standards is something entirely different.

This is where performance certification becomes important.

EN 60079-29-1: Performance Certification for Fixed Flammable Gas Detectors

For fixed gas detectors intended for explosive atmospheres, EN 60079-29-1 defines the general and performance requirements for detectors designed to measure flammable gases.

A detector certified according to this standard has undergone independent testing to verify critical performance characteristics, including:

• Response time
• Measurement accuracy
• Signal stability
• Performance under defined environmental conditions

These are not simply manufacturer claims but independently validated results obtained through testing by an accredited certification body.

An important point should be emphasised.

EN 60079-29-1 certifies detector performance for specific target gases under defined testing conditions.

It does not certify a detector universally for every gas or every application.

Therefore, during system specification, engineers should always verify that the detector's certified performance covers the actual gases present within the facility.

This distinction matters because every gas behaves differently.

Gas density, dispersion characteristics, sensor response, measurement stability, and response time all vary depending on the gas being monitored.

For this reason, referring simply to a "gas detector" is often insufficient.

A detector should always be evaluated according to the gases for which its performance has been certified and the measurement ranges it has been independently validated to monitor.

Ultimately, this is a matter of engineering responsibility.

It is not enough to confirm that a detector is suitable for installation in a hazardous area. Engineers must also ensure that its detection performance has been independently certified for the specific hazards present within the plant.

Maintenance: The Real Test of a Fixed Gas Detector

Certifications are verified before installation.

Maintenance is what determines whether a detector remains practical and reliable throughout its operational life.

In hazardous areas, even routine servicing is never a trivial task.

Any fixed gas detector installed in an ATEX environment is subject to strict regulatory requirements for inspection, calibration, and sensor replacement. Every maintenance activity must follow established procedures, be carried out by qualified personnel, and use appropriate equipment.

This is where the true maintainability of a detector becomes evident—far beyond what can be learned from a technical datasheet.

Sensor Replacement in Hazardous Areas

Sensor replacement is often the most critical maintenance operation.

With conventional fixed gas detectors, replacing the sensor usually requires opening the flameproof enclosure. In hazardous areas, this introduces additional challenges, including compliance with explosion-protection procedures, the risk of damaging seals or threaded joints, and a problem that field technicians know all too well: after years of operation, the detector head can seize onto the enclosure, making removal extremely difficult—or even impossible.

The Tecnocontrol GDS850 addresses this issue through a dedicated modular design.

Its sensor cartridge can be replaced via an integrated plug-in socket without opening the flameproof enclosure.

The procedure is comparable to replacing a modular electronic component: fast, controlled, and requiring no special tools.

The result is a significant reduction in maintenance time, lower servicing costs, and fewer risks associated with opening an explosion-proof enclosure in hazardous locations.

For this reason, maintainability should be considered from the very beginning of the product selection process.

It is not a secondary feature—it is one of the clearest indicators of whether a gas detector has been designed simply to meet certification requirements or to remain efficient and serviceable throughout its entire operating life.

Diagnostics and Sensor Management

One of the biggest challenges in gas detection systems is uncertainty.

Without reliable diagnostic information, operators cannot accurately determine the condition of the sensing element, whether the detector requires maintenance, or whether it is still operating within its specified performance parameters.

This uncertainty typically leads to one of two undesirable outcomes:

• maintenance is performed too frequently as a precaution, increasing operating costs; or
• servicing is delayed because the detector appears to be functioning correctly, even though the sensor may fail before the next scheduled inspection.

Integrated diagnostics fundamentally change this approach.

A detector capable of displaying sensor operating hours, estimated remaining service life, and real-time operating status enables maintenance decisions to be based on objective data rather than assumptions.

Maintenance becomes predictive instead of reactive.

The Tecnocontrol GDS850 is available both with and without an integrated display.

The display version includes Bluetooth® connectivity, allowing users to access a dedicated mobile application that provides comprehensive diagnostic information without opening the enclosure.

Using the app, maintenance personnel can:

• monitor sensor operating parameters;
• check relay alarm thresholds;
• perform electrical verification tests;
• review the detector's complete diagnostic status.

In hazardous areas, carrying out these operations without opening the flameproof enclosure is more than a convenience.

It significantly reduces operational risks while simplifying maintenance procedures and helping maintain compliance with explosion-protection requirements.

For engineering companies and maintenance contractors responsible for facilities with multiple detection points, diagnostics also improve documentation and traceability.

Knowing when the last inspection was performed, recording operating parameters, and monitoring the remaining service life of each sensor are essential elements of an effective asset management strategy.

During audits or regulatory inspections, documented maintenance records provide objective evidence that maintenance activities have been properly planned and executed—not merely assumed.

Total Cost of Ownership: The Purchase Price Doesn't Tell the Whole Story

The cost of an industrial ATEX gas detector extends far beyond its purchase price.

The initial investment represents only a fraction of the overall expense.

Throughout its service life, the detector will require installation, commissioning, periodic testing, maintenance, calibration, repairs, and eventually sensor replacement.

For this reason, gas detector selection should always be evaluated in terms of Total Cost of Ownership (TCO).

Many of the factors that determine lifecycle costs never appear in a product datasheet, including:

• maintenance frequency;
• plant downtime;
• labour costs for qualified personnel working in hazardous areas;
• spare parts availability and cost;
• whether maintenance requires replacement of the entire detector head or only the sensing element.

In hazardous areas, every maintenance intervention is inherently more expensive.

Specialist personnel, strict safety procedures, work permits, and extended intervention times all contribute to higher operating costs.

A detector that requires complete disassembly of the flameproof enclosure simply to replace a sensor will inevitably generate higher maintenance costs than one designed with a modular replacement system.

When multiplied across dozens—or even hundreds—of detection points over the lifetime of an industrial facility, these differences become substantial.

The Tecnocontrol GDS850 has been designed with this lifecycle perspective in mind.

Features such as its replaceable sensor cartridge, flexible cable entry configuration, integrated communication interfaces, and Bluetooth diagnostics are not merely technical specifications.

They directly reduce maintenance time, simplify field operations, and minimise uncertainty throughout the detector's operational life.

Evaluating Total Cost of Ownership means asking a different question.

Instead of asking:

"How much does this detector cost?"

the more meaningful question becomes:

"How much will it cost to install, maintain, and operate correctly throughout its entire service life?"

That is the question that distinguishes a detector that appears economical on paper from one that delivers genuine long-term value in the field.

How to Choose a Fixed Gas Detector for Hazardous Areas: A Practical Checklist

As we've seen, selecting a fixed gas detector for hazardous areas involves much more than verifying regulatory compliance.

The right choice depends on how the detector will perform throughout its entire lifecycle—from installation and system integration to routine maintenance and long-term operating costs.

The checklist below summarises the key criteria to evaluate before specifying or installing a fixed gas detection system.

Fixed Gas Detector Selection Checklist for Hazardous Areas

Certifications

✔ ATEX certification appropriate for the hazardous area classification (for example, Zone 1 for areas where explosive atmospheres may occur during normal operation).

✔ IECEx certification for international projects, global procurement specifications, or facilities subject to international audits.

✔ EN 60079-29-1 performance certification covering the specific target gases present within the plant.

Functional Safety

✔ Declared and independently certified SIL rating, with SIL 2 hardware representing the maximum achievable level for an individual detector.

✔ Assessment of redundant system architecture where a higher overall Safety Integrity Level is required.

Installation

✔ Number and positioning of cable entries.

✔ Flexible mounting options and detector orientation suitable for the actual installation layout.

System Integration

✔ 4–20 mA analogue output compatible with the existing gas controller or interface module.

✔ Modbus RS485 communication for PLC and SCADA integration.

✔ Availability of standard or SIL-certified relay outputs, depending on the functional safety requirements of the system.

✔ Separate management of alarm and fault signals.

Maintenance and Diagnostics

✔ Sensor replacement without opening the flameproof enclosure.

✔ Integrated diagnostics providing sensor operating hours, estimated remaining service life, and operating status.

✔ Ability to perform non-intrusive verification without opening the enclosure.

✔ Availability and cost of spare parts.

Total Cost of Ownership

✔ Estimated maintenance costs over the entire service life of the installation.

✔ Cost comparison between replacing only the sensing element and replacing the complete detector head.

Conclusion

Selecting a fixed gas detector for hazardous areas should never be based solely on regulatory compliance.

ATEX certification is essential, but it represents only the starting point.

Installation flexibility, certified performance, functional safety, ease of maintenance, diagnostic capabilities, and lifecycle costs all have a direct impact on the reliability and long-term value of the gas detection system.

Considering these aspects during the specification stage helps engineers, system integrators, and plant operators reduce operational risks, simplify maintenance activities, and optimise the total cost of ownership throughout the life of the installation.

The Tecnocontrol GDS850 has been engineered with each of these requirements in mind.

It combines ATEX and IECEx certification, SIL 2 hardware and SIL 3 software certification, EN 60079-29-1 certified performance, four cable entries for maximum installation flexibility, 4–20 mA and Modbus RS485 communication, optional standard or SIL-certified relay outputs, a replaceable plug-in sensor cartridge that eliminates the need to open the enclosure, and integrated Bluetooth diagnostics for faster, safer maintenance.

Whether you're designing a new gas detection system or upgrading an existing installation, evaluating these features as part of your specification process can significantly improve both operational reliability and long-term maintenance efficiency.

To learn more about the Tecnocontrol GDS850, download the complete technical datasheet or contact our engineering team to discuss the most suitable configuration for your application.