CAN CSA C22.2 No. 60079-11-14 (2018): Equipment Protection by Intrinsic Safety for Hazardous Locations

Introduction

CAN CSA C22.2 No. 60079-11-14 (2018) is the Canadian adoption of IEC 60079-11, forming part of the CSA C22.2 series under the Canadian Electrical Code, Part II (CEC Part II). This standard specifies the requirements for construction and testing of electrical equipment intended for use in explosive atmospheres, where protection is achieved by limiting electrical energy (voltage, current, and stored charge) to a level below that which can cause ignition of a flammable gas, vapour, or dust under normal operation, single fault, or rare fault conditions.

Commonly referred to as “Intrinsic Safety” (Ex i), this protection method is widely applied in instrumentation, control systems, sensors, and actuators installed in classified areas such as oil refineries, chemical plants, grain handling facilities, and mines. The standard harmonizes Canadian requirements with international practice, facilitating global trade and acceptance while ensuring the rigorous safety level demanded by the CEC.

Scope and Application

CAN CSA C22.2 No. 60079-11-14 applies to electrical equipment that is intended for use in explosive gas atmospheres (Zone 0, Zone 1, Zone 2) and explosive dust atmospheres (Zone 20, Zone 21, Zone 22), where the equipment itself or its interconnections must not release sufficient electrical energy to cause ignition.

The standard covers:

• Apparatus rated for use as intrinsically safe equipment (field devices).
• Associated apparatus (e.g., galvanic isolators, zener barriers, shunt-diode barriers) that limit energy.
• Systems comprising intrinsically safe and associated apparatus interconnected by certified cables.

Excluded from scope are equipment relying solely on other protection techniques (e.g., flameproof enclosure, increased safety), equipment for ignition of flammable gases only (dust requirements are referenced in CEC Part I), and equipment operating above AC 660 V or DC 660 V unless specially evaluated.

Technical Requirements

Levels of Protection (ia, ib, ic)

The standard defines three levels of intrinsic safety protection, each corresponding to the acceptable number of faults and the resulting safety integrity. The selection of level depends on the zone classification and risk assessment.

For dust atmospheres, similar levels (Ex ia D, Ex ib D, Ex ic D) apply, referencing dust ignition test requirements.

Entity Parameters and System Assessment

CAN CSA C22.2 No. 60079-11-14 introduces the concept of entity parameters for intrinsically safe apparatus and associated apparatus. The safety of any fieldbus or loop is verified by ensuring that the energy-limited output of the associated apparatus does not exceed the capacity of the field device:

• V_oc (open-circuit voltage) ≤ V_max of field device
• I_sc (short-circuit current) ≤ I_max of field device
• P_o (output power) ≤ P_i of field device
• C_a (allowable external capacitance) ≥ C_i + C_cable
• L_a (allowable external inductance) ≥ L_i + L_cable

These parameters must be documented for each piece of apparatus and verified during system design and certification.

Construction and Component Requirements

The standard imposes strict requirements on components, spacing, encapsulation, and creepage/clearance distances to prevent short circuits and failures that could increase energy levels. Key elements include:

• Printed board spacing: Minimum 1.6 mm between conductors of opposite polarity under 250 V; larger for higher voltages.
• Fusing: Redundant or non-resettable fuses for fault current limitation.
• Encapsulation: For Ex ia and Ex ib, certain circuits must be encapsulated to protect against capacitance and inductance shortfalls.
• Safety barriers: Zener diodes or optocouplers must be tested to ensure they fail open-circuit or short-circuit only in a controlled manner.
• Temperature classification: The maximum surface temperature of any component (including in normal and fault conditions) must not exceed 85°C for T6 or 100°C for T5 etc., depending on the gas group temperature class (T1–T6).

Temperature Classification

Equipment covered by this standard is assigned a temperature class (T1…T6) based on the maximum surface temperature attained under specified fault conditions. The following table summarizes typical temperature classes and their maximum allowed temperature:

For dust atmospheres, the maximum surface temperature is also limited to the ignition temperature of the dust cloud or layer, as specified in IEC 60079-14.

Implementation Highlights

Implementing CAN CSA C22.2 No. 60079-11-14 into product development requires careful attention at all stages, from circuit design to production testing. Below are key considerations:

System Design Approach

Design engineers must adopt a system-level view: the intrinsic safety loop consists of an associated apparatus (barrier/isolator), cabling, and the field device itself. The combination must satisfy the entity parameter criteria under both normal and fault conditions.

• Use certified safety barriers that match the gas group (I, IIA, IIB, IIB+H₂, IIC) and temperature class.
• Consider cable parameters (capacitance per unit length and inductance per unit length); long cables can exceed the allowed energy limits.
• Ensure that the apparatus can withstand a fault (e.g., component short) without exceeding ignition curves for the specific gas/air mixture.

Certification and Marking

All intrinsically safe equipment must be certified by an accredited certification body (e.g., CSA, UL, Intertek) to this standard. Marking requirements include:

• Manufacturer’s name and product identifier.
• Standard reference: e.g., CAN CSA C22.2 No. 60079-11-14.
• Ex marking symbol: Ex ia IIC T4, Ex ib IIB T6, etc.
• Entity parameters (V_max, I_max, C_i, L_i).
• Specific conditions of safe use (X mark).

Compliance and Certification Notes

Manufacturers seeking compliance with CAN CSA C22.2 No. 60079-11-14 should be aware of the following:

• Differences from IEC 60079-11:2011: The Canadian edition includes national differences (Annex NA) covering voltage thresholds for dust apparatus, additional requirements for mining (DBR 1339), and references to CEC Part I installation rules. These must be incorporated.
• Relationship to other CSA standards: Equipment may also need to comply with CAN CSA C22.2 No. 60079-0 (general requirements) and applicable product-specific standards.
• CSA Listing: Many certification bodies maintain product listings that are accepted across Canada under the Canadian Electrical Code. Ensure the certification mark (e.g., CSA or cCSAus) includes the Ex mark.
• Periodic audits: Once certified, manufacturers must undergo factory inspections to verify ongoing conformity. Record keeping of critical component sourcing and production tests is mandatory.

Frequently Asked Questions

Technical Article – 2026