Common PCB Design Mistakes for Intrinsically Safe Equipment

28 Aug 2026

Tips for Reducing Redesigns and Streamlining Certification

Designing an intrinsically safe product involves much more than selecting the right components. The printed circuit board (PCB) layout itself plays a critical role in demonstrating compliance with IEC 60079-11 standard. A design that functions perfectly in the laboratory may still fail certification if the PCB does not adequately control the risk of ignition under normal operation and fault conditions. Many certification issues can be avoided by considering intrinsic safety requirements early in the PCB design process. This article highlights several common PCB design mistakes and offers practical recommendations to help reduce redesigns and streamline certification.

Insufficient Creepage and Clearance Distances

One of the most common issues identified during design reviews is inadequate spacing between conductive parts. Intrinsic safety requires sufficient separation between circuits of different potentials to prevent arcing or breakdown, especially when fault conditions are considered. Designers often optimize layouts for compactness without realizing that the available spacing may not satisfy the minimum requirements specified in IEC 60079-11.

Typical problem areas include:

• High-voltage traces routed too close to intrinsically safe circuits
• Insufficient spacing around connectors
• Insufficient spacing beneath components
• Reduced spacing caused by copper pours

Design Tip: Determine the required creepage and clearance distances early in the layout process. Verify spacing after the PCB is complete to make sure it complies with IEC 60079-11.

Ignoring Fault Conditions During Layout

A PCB should not only operate safely during normal operation, it must also remain safe when specified faults occur. For example, consider what happens if:

• A resistor becomes short-circuited
• A transistor fails
• A Zener diode opens
• Adjacent traces become bridged by conductive contamination

If a single fault allows excessive voltage or current to reach an intrinsically safe circuit, the design may not comply with IEC 60079-11.

Design Tip: During PCB reviews, evaluate how electrical faults could propagate through the layout rather than considering only the schematic.

Mixing Intrinsically Safe and Non-Intrinsically Safe Circuits

Many products contain both intrinsically safe and non-intrinsically safe circuits on the same PCB. Problems often arise when:

• The two circuit types share routing channels
• Traces cross unnecessarily
• Copper areas overlap
• Connectors are positioned without adequate segregation

Poor segregation increases the likelihood that faults could transfer hazardous energy into the intrinsically safe portion of the circuit.

Design Tip: Physically separate IS and non-IS circuitry wherever practical. Keeping the two sections visually distinct also simplifies certification reviews.

Excessive Component Surface Temperatures

Intrinsic safety is not only about preventing sparks. Excessive component temperatures can also ignite hazardous atmospheres. Designers often focus on electrical ratings while overlooking thermal performance. Examples include:

• Resistors operating exceed their limits
• MOSFETs dissipating significant power
• Voltage regulators with insufficient copper area for heat dissipation

These hot components may exceed the equipment's required temperature class.

Design Tip: Identify components with significant power dissipation early in the design and perform thermal analysis under worst-case operating and fault conditions.

Poor Grounding Strategy

Grounding is essential for circuit functionality, but inappropriate ground layouts can create unexpected current paths. Examples include:

• Shared return paths between IS and non-IS circuits
• Large ground loops
• Multiple uncontrolled connections between reference grounds

These conditions can complicate fault analysis and introduce unexpected energy transfer mechanisms.

Design Tip: Clearly define grounding architecture during schematic development rather than leaving it to PCB layout.

Excessive Stored Energy

Capacitors and inductors can store sufficient energy and may become an ignition source. The total stored energy must remain within acceptable limits under both normal and fault conditions in accordance with IEC 60079-11.

Design Tip: Review every energy storage element during design and understand how it contributes to the overall intrinsic safety assessment.

Waiting Until the End to Consider Certification

Perhaps the most expensive mistake is treating intrinsic safety as a final approval step rather than a design requirement. When compliance is evaluated only after prototype completion, engineers may discover issues such as:

• Insufficient spacing
• Incorrect component ratings
• Inadequate fault protection
• Thermal non-compliance

Resolving these issues often requires a complete PCB redesign.

Design Tip: Involve your certification team or compliance engineer during schematic and layout reviews. Early feedback is significantly less expensive than redesigning finished hardware.

Final Thoughts

Successful intrinsically safe products are rarely achieved by chance. They result from safety considerations into every stage of the design process – from component selection and schematic design to PCB layout and ignition risk evaluation.

While every product presents unique challenges, many certification delays from the same recurring issues: exceeded components ratings, inadequate spacing, overlooked fault conditions, and insufficient attention to energy limitation.

By addressing these considerations early, design teams can reduce redesign cycles, simplify certification, and bring compliant products to market more efficiently. A well-designed layout not only improves electrical performance but also demonstrates that hazardous ignition risks have been effectively controlled.