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Comprehensive Guide to CAN CSA C22.2 No. 60079-28-16: Protection of Equipment Using Optical Radiation in Explosive Atmospheres
Understanding the Canadian Standard for Optical Radiation Protection in Hazardous Locations
Scope and Introduction
CAN CSA C22.2 No. 60079-28-16, entitled “Explosive atmospheres – Part 28: Protection of equipment and transmission systems using optical radiation”, is the Canadian adoption of the international standard IEC 60079-28:2015 with prescribed national deviations for Canada. It forms part of the extensive suite of explosive atmosphere standards under the Canadian Electrical Code, Part II (C22.2 series), and serves as a critical reference for designers, manufacturers, installers, and certifiers of equipment that uses optical radiation in or near hazardous locations.
This standard specifies the requirements for equipment and transmission systems where optical radiation (ultraviolet, visible, or infrared) is employed, and the optical radiation itself presents a potential ignition source for explosive gas, vapor, mist, or dust atmospheres. It defines three distinct types of protection applicable to optical equipment and systems:
- op is – optical radiation with intrinsic safety (incapable of causing ignition due to inherently low power or energy)
- op pr – optical radiation with protected device (contained within an enclosure that prevents the optical radiation from escaping under normal and fault conditions)
- op sh – optical radiation with shutdown (the optical radiation is automatically interrupted before it can reach a hazardous level)
The standard covers equipment such as LEDs, lasers, optical-fiber communication systems, optical sensors, and any other apparatus that generates, transmits, or receives optical radiation in a potentially explosive environment. It also addresses optical-fiber cables, connectors, and associated passive components.
Note: CAN CSA C22.2 No. 60079-28-16 is intended to be used in conjunction with the common requirements of CAN CSA C22.2 No. 60079-0 (Explosive atmospheres – Part 0: Equipment – General requirements) and relevant installation standards such as CAN CSA C22.2 No. 60079-14 (Electrical installations design, selection and erection) and CAN CSA C22.2 No. 60079-17 (Inspection and maintenance).
Technical Requirements and Protection Concepts
Classification of Optical Radiation Protection
The standard establishes three protection concepts that are applied based on the optical power and the likelihood of an explosive atmosphere being present. The table below provides a technical comparison.
| Symbol | Protection Concept | Principle | Typical Applications |
|---|---|---|---|
| op is | Optical radiation with intrinsic safety | Optical power/energy is limited below the minimum ignition energy (MIE) of the surrounding atmosphere, even under single or multiple fault conditions. | Low-power fiber-optic sensors, LED indicators, optical communication links in Zone 0/20 locations. |
| op pr | Optical radiation with protected device | The optical source and transmission path are enclosed within a robust enclosure that prevents the escape of optical radiation capable of causing ignition. The enclosure is designed to withstand internal explosions or ingress of the explosive atmosphere. | High-power lasers used in material processing, optical pyrometers, gas-analysis equipment in Zones 1/21 or 2/22. |
| op sh | Optical radiation with shutdown | A monitoring subsystem detects conditions that could lead to hazardous optical radiation (e.g., fiber break, loss of containment) and automatically interrupts the optical power before ignition can occur. | High-power fiber-optic transmission systems, remote optical powering of sensors, laser-based measurement systems with fault-tolerant shutdown logic. |
Optical Power and Energy Limits
The standard specifies maximum permissible optical power levels depending on the wavelength, mode of operation (continuous wave or pulsed), and the classification of the surrounding explosive atmosphere (gas groups, dust layers, etc.). These limits are derived from experimental ignition data and are generally consistent with IEC 60079-28:2015. Key technical parameters include:
- Optical power limits for op is: Continuous-wave (CW) optical power ≤ 35 mW for wavelengths 400–700 nm; more restrictive for longer wavelengths due to higher absorption in dust atmospheres.
- Pulsed systems: Peak power and pulse energy are limited such that the total energy per pulse is below the MIE of the most sensitive gas group present (typically Group IIC, ethylene, or hydrogen).
- Optical density for op pr enclosures: Enclosure must achieve an optical density (OD) sufficient to attenuate any escaping optical radiation to safe levels during normal operation and after defined faults.
- Shutdown reaction time for op sh: The system must detect a fault and completely remove optical power within a time that prevents ignition – typically less than 100 ms for gas atmospheres and less than 1 s for dust atmospheres.
Critical: Engineers must verify that optical power limits are not exceeded under any foreseeable fault condition. Over-reliance on single-fault criteria without considering multiple independent faults is a common pitfall.
Fiber Optic Cable and Connector Requirements
The standard imposes stringent requirements on the passive optical components used in hazardous locations:
- Cables must be resistant to the environmental conditions (temperature, chemicals, mechanical stress) and must not propagate an explosion through the fiber core or cladding.
- Connectors that are routinely disconnected in a hazardous area must be designed such that they cannot produce an ignition-capable spark or hot surface, and they must incorporate features to prevent the emission of hazardous optical radiation upon disconnection.
- All passive components must be tested in accordance with the applicable clauses of IEC 60079-28:2015, including verification of optical loss and mechanical durability.
Implementation Highlights
Implementing CAN CSA C22.2 No. 60079-28-16 requires a holistic system-level approach. The following highlights address practical aspects:
System Design Considerations
- Wavelength and power selection: Choose optical sources and detectors that inherently comply with op is limits wherever possible to simplify certification and reduce system cost.
- Fault analysis: Perform a comprehensive failure mode and effects analysis on the optical path, considering fiber breaks, connector degradation, source driver faults, and environmental degradation.
- Redundancy for op sh: The shutdown mechanism must be self-monitoring (fail-safe) and should be verified at least as frequently as required by the inspection schedule of the installation standard.
- Integration with other protection types: Optical components may be combined with explosion-proof enclosures (Ex d) or increased safety (Ex e) provided the optical path itself remains compliant with the optical radiation protection concept.
Testing and Verification
Testing under CAN CSA C22.2 No. 60079-28-16 typically includes:
- Optical power measurement: Under normal and worst-case fault conditions.
- Enclosure tests (for op pr): Impact resistance, ingress protection, and pressure test if the enclosure relies on explosion containment.
- Shutdown time test (for op sh): Verify that the optical power is removed within the specified time after introduction of a simulated fault.
- Environmental conditioning: Temperature cycling, humidity, and vibration to ensure optical performance does not degrade to unsafe levels over the equipment lifetime.
Tip: Early engagement with a recognized certification body (e.g., CSA Group, UL, Intertek) is strongly recommended to clarify the scope of required testing and to ensure that any national deviations for Canada are properly addressed.
Compliance Notes and Canadian Particularities
Adoption of IEC 60079-28:2015 with Canadian National Deviations
CAN CSA C22.2 No. 60079-28-16 is identical to IEC 60079-28:2015 except for a limited number of national deviations that reflect Canadian regulatory and climatic conditions:
- Ambient temperature range: The standard explicitly covers an extended ambient temperature range of –40 °C to +60 °C for equipment installed in Canada, unless otherwise specified by the manufacturer.
- Wiring and termination requirements: Additional requirements for conductor sizes and grounding in accordance with the Canadian Electrical Code, Part I (CSA C22.1).
- Climatic conditions: Recognition of extreme humidity, ice loading, and ultraviolet exposure for outdoor installations.
- Marking: Equipment certified to the Canadian standard must bear the CSA mark and the standard number “C22.2 No. 60079-28-16” along with the protection concept symbol (e.g., Ex op is IIC T6).
Relationship to the Canadian Electrical Code
As part of the C22.2 series, compliance with this standard is generally required for equipment to be installed in accordance with the CE Code, Part I. It is also referenced by provincial and territorial regulations for hazardous locations. Manufacturers seeking CSA certification must demonstrate compliance with all applicable parts of the C22.2 suite, particularly C22.2 No. 60079-0 (general requirements) and C22.2 No. 60079-14 (installation design).
Key Benefit: Using the CAN CSA C22.2 version ensures seamless acceptance across all Canadian jurisdictions without the need for additional testing or paperwork because the standard is harmonized with the overarching national electrical safety framework.
Field Installation and Maintenance
Installers must consult the equipment’s certificate and follow any specific instructions related to the optical path. Regular inspection of optical connectors, cables, and shutdown systems is essential, especially in dusty or corrosive environments. The standard recommends that maintenance personnel be trained to recognize optical hazards and to follow lockout/tagout procedures for optical systems.
Warning: Never look directly into a fiber endface or expose a cable during operation unless the system is verified to be compliant with op is limits. Even low-power optical radiation can cause eye damage, and if the optical path is not completely enclosed, it may create an ignition source in a flammable atmosphere.
Conclusion
CAN CSA C22.2 No. 60079-28-16 provides a robust framework for the safe use of optical radiation in explosive atmospheres across Canada. By clearly defining three protection concepts (op is, op pr, op sh) and setting rigorous limits on optical power and shutdown performance, the standard enables designers to harness the advantages of fiber‑optic communication, laser-based sensing, and optical power transmission while maintaining the highest level of safety. Compliance with the standard, along with its companion C22.2 explosive atmosphere standards, is essential for manufacturers, system integrators, and end users operating in hazardous locations.
Q: What is the difference between op is, op pr, and op sh?
A: op is relies on inherent optical power limitation below ignition energy (similar to intrinsic safety for electrical circuits). op pr contains the optical radiation within a robust enclosure that prevents escape of ignition-capable radiation. op sh uses an automatic shutdown system that interrupts hazardous optical radiation before ignition can occur. Each concept is suitable for different power levels and location zones.
A: op is relies on inherent optical power limitation below ignition energy (similar to intrinsic safety for electrical circuits). op pr contains the optical radiation within a robust enclosure that prevents escape of ignition-capable radiation. op sh uses an automatic shutdown system that interrupts hazardous optical radiation before ignition can occur. Each concept is suitable for different power levels and location zones.
Q: Is CAN CSA C22.2 No. 60079-28-16 mandatory in Canada?
A: Yes, for equipment intended for explosive atmospheres, compliance with the relevant C22.2 hazardous location standards is typically mandatory under provincial and territorial regulations that adopt the Canadian Electrical Code. Equipment certified to this standard is recognized across Canada without further testing.
A: Yes, for equipment intended for explosive atmospheres, compliance with the relevant C22.2 hazardous location standards is typically mandatory under provincial and territorial regulations that adopt the Canadian Electrical Code. Equipment certified to this standard is recognized across Canada without further testing.
Q: How does this standard relate to the international IEC version?
A: CAN CSA C22.2 No. 60079-28-16 is the Canadian adoption of IEC 60079-28:2015 with a few national deviations (e.g., extended ambient temperature range, Canadian wiring requirements). Equipment that meets the IEC version may still require supplementary testing or marking to be accepted in Canada unless it carries a valid CSA certification to the C22.2 standard.
A: CAN CSA C22.2 No. 60079-28-16 is the Canadian adoption of IEC 60079-28:2015 with a few national deviations (e.g., extended ambient temperature range, Canadian wiring requirements). Equipment that meets the IEC version may still require supplementary testing or marking to be accepted in Canada unless it carries a valid CSA certification to the C22.2 standard.
Q: What marking must appear on certified equipment?
A: The equipment must bear the CSA mark, the standard number “C22.2 No. 60079-28-16”, the protection concept symbol (e.g., Ex op is IIC T6), and the manufacturer’s name, model, and rated parameters. The marking must be durable and legible for the life of the equipment.
A: The equipment must bear the CSA mark, the standard number “C22.2 No. 60079-28-16”, the protection concept symbol (e.g., Ex op is IIC T6), and the manufacturer’s name, model, and rated parameters. The marking must be durable and legible for the life of the equipment.
This article provides general guidance and is not a substitute for the official standard. Always consult the current edition of CAN CSA C22.2 No. 60079-28-16 and the Canadian Electrical Code for full requirements. | Updated 2026