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CAN CSA C22.2 No. 60079-2-16: Pressurized Enclosures for Explosive Atmospheres
Technical Requirements and Implementation Guide for Type ‘p’ Protection in Hazardous Locations
Introduction and Scope
The standard CAN CSA C22.2 No. 60079-2-16 is a national adoption of the international standard IEC 60079-2:2016 by the Canadian Standards Association (CSA Group). It belongs to the C22.2 family of Canadian Electrical Code, Part II standards, covering equipment for use in hazardous (classified) locations.
This standard specifies the requirements for the design, construction, testing, and marking of electrical equipment protected by pressurized enclosures (type ‘p’) intended for use in explosive gas or combustible dust atmospheres. The primary principle of this protection method is to prevent the ingress of a surrounding explosive atmosphere into an enclosure by maintaining a protective gas (air or inert gas) at a pressure higher than that of the ambient atmosphere.
The scope includes:
- Equipment for Zones 1, 2, 21, and 22, and for equipment protection level (EPL) Gb, Gc, Db, Dc as applicable
- Pressurization systems using air or inert gas
- Internal components that may release flammable substances into the enclosure
- Monitoring and control devices for pressure, flow, and temperature
- Combined protections, such as pressurized enclosures containing other Ex components
It is important to note that this standard does not cover pressurized enclosures for group I (mining) or equipment that relies on spark-proof construction alone. It also does not address the specific requirements for rooms or analyser houses, which are covered separately.
Tip: CAN CSA C22.2 No. 60079-2-16 is essentially identical to IEC 60079-2:2016 but includes Canadian national modifications (e.g., referencing the Canadian Electrical Code, Part I). Always verify the specific CSA edition for regional differences before designing for the Canadian market.
Technical Requirements
Design and Construction
Enclosures must be designed to withstand the overpressure generated by the pressurization system, typically a minimum of 0.5 mbar (50 Pa) above the surrounding pressure. For gas groups, the maximum surface temperature of the enclosure must not exceed the ignition temperature of the gas or vapour. For dust applications, the surface temperature must remain below the dust layer ignition temperature.
The standard requires that the enclosure and all its components (windows, doors, conduit entries) have a degree of ingress protection appropriate to the environment — at least IP4X for gas and IP6X for dust (where applicable). Seams, joints, and seals must be designed to prevent leakage that could compromise pressurization.
Pressurization Systems
CAN CSA C22.2 No. 60079-2-16 categorizes pressurization into three types for gas atmospheres and one for dust:
| Type | EPL | Zone Applicability | Description |
|---|---|---|---|
| px | Gb | Zone 1, 2 | Pressurization with internal release; continuous monitoring of pressure and purging before energization |
| py | Gb | Zone 1, 2 | Pressurization with limited internal release; reduced purging requirements |
| pz | Gc | Zone 2 | Pressurization for normal operation without ignition source inside; no internal release |
| pD | Db / Dc | Zone 21, 22 | Pressurization for combustible dust; includes spark prevention and dust-tightness |
Internal Releases and Monitoring
For types px and py, the equipment inside the enclosure may release flammable gases or liquids during normal operation. The standard prescribes requirements for:
- Purging: Before energy is applied, a sufficient volume of protective gas must pass through the enclosure to reduce the concentration of any flammable mixture below 25% of the Lower Explosive Limit (LEL).
- Overpressure monitoring: A pressure switch or transmitter shall continuously monitor the internal pressure. If pressure falls below the minimum, protective action (alarm or power disconnection) must be initiated.
- Flow monitoring (for pressurized systems using a protective gas source): A flow sensor ensures that the required exchange of gas is maintained even with small leaks.
Warning: Incorrect calibration of pressure and flow sensors is a common cause of certification failure. Ensure that all monitoring devices are rated for the applicable SIL or reliability levels as required by the standard and referenced by CSA C22.2 No. 60079-2-16.
Dust-Specific Requirements (pD)
For dust atmospheres, the pressurization system is similar but must also prevent dust ingress and limit surface temperature under all operating conditions. The enclosure must be dust-ignition-proof (IP6X). The pressurization is monitored; loss of pressure initiates an alarm or disconnection. The standard also requires that the enclosure design prevents static electricity accumulation that could ignite dust clouds.
Implementation Highlights
When implementing a type ‘p’ solution in accordance with CAN CSA C22.2 No. 60079-2-16, several practical aspects deserve special attention:
System Components
Pressurization systems can be integrated in the equipment (e.g., an Ex p enclosure with a built-in purging/pressurization controller) or supplied as separate units. Both approaches must be certified as a system together. Key components include:
- Protective gas supply (quality, pressure, flow rate)
- Purging solenoid, pressure sensor, flow switch
- Control unit with safeguards (e.g., time delay for purging)
- Sealing gaskets, compression fittings, cable glands
Marking and Documentation
Each certified assembly must be marked with the Ex marking, type of protection, applicable gas groups (e.g., IIB + H₂), temperature class (e.g., T4), and the standard number CAN CSA C22.2 No. 60079-2-16. The manufacturer must provide instruction manuals including:
- Details on pressurization gas quality (e.g., air, nitrogen)
- Minimum and maximum pressure values
- Purging time and volume
- Maintenance and inspection intervals
- Data on internal releases (if applicable)
Best Practice: To simplify installation, consider using pre-certified pressurization control modules that comply with CAN CSA C22.2 No. 60079-2-16. These units typically include all required sensors, timing relays, and certified enclosures, reducing engineering effort and validation costs.
Compliance and Certification Notes
For the Canadian market, compliance with CAN CSA C22.2 No. 60079-2-16 is mandatory for equipment used in hazardous locations as defined by the Canadian Electrical Code, Part I (CSA C22.1). Certification is typically performed by an accredited certification body (CB) such as CSA Group, Intertek (ETL), or Underwriters Laboratories of Canada (UL). The process includes:
- Design review: Verification of enclosure strength, pressurization system design, monitoring circuits, and documentation.
- Type testing: Overpressure testing, purging efficiency verification, leakage rate measurement, and temperature rise under normal and fault conditions.
- Prototype inspection: Visual and dimensional checks against drawings, marking, and installation instructions.
- Factory production control (FPC): Audit of manufacturing processes to ensure consistent quality.
It is important to note that CAN CSA C22.2 No. 60079-2-16 may include Canadian deviations from IEC 60079-2:2016. For example, the standard references Canadian ambient temperature ranges (typically –25 °C to +40 °C, but other ranges acceptable) and specific requirements for grounding and bonding. Also, the standard may mandate a different level of protection for certain zones compared to the IEC version. Always refer to the latest CSA edition (e.g., 2016 edition plus any amendments).
Critical: If the standard is used for combustible dust (pD), the installation must comply with the Canadian Electrical Code requirements for Class II, Division 1 or 2, or Zone 21/22. The interaction between pressurization and dusting must be carefully evaluated to avoid accumulation of dust on heat-producing surfaces. Frequent cleaning or the use of inert gas may be necessary.
For multinational projects, equipment certified to IEC 60079-2:2016 may be accepted in Canada if it complies with the national deviations. However, due to differences in wiring requirements and voltage ratings, it is safer to obtain CSA-specific certification for permanent installations.
Transition Periods and Updates
As of 2026, the current edition remains CAN CSA C22.2 No. 60079-2-16, with no amended version yet published. However, users should monitor CSA Group for new editions or amendments that may align with the upcoming IEC 60079-2 change cycle. When the IEC standard is revised, CSA typically adopts the changes within a few years.
Frequently Asked Questions
Q: What is the difference between type px and py pressurization according to CAN CSA C22.2 No. 60079-2-16?
A: Type px allows internal release of flammable substances (e.g., from a gas analyzer) and requires full purging with continuous overpressure monitoring. Type py permits limited internal release (reduced risk) and may have less stringent purging requirements. In practice, px is for higher risk applications, while py is used when the internal release is negligible.
A: Type px allows internal release of flammable substances (e.g., from a gas analyzer) and requires full purging with continuous overpressure monitoring. Type py permits limited internal release (reduced risk) and may have less stringent purging requirements. In practice, px is for higher risk applications, while py is used when the internal release is negligible.
Q: Can CAN CSA C22.2 No. 60079-2-16 be used for Zone 0 equipment?
A: No. Type ‘p’ pressurization is not allowed as a sole protection method for Zone 0 (in gas) or Zone 20 (in dust). The standard covers Zone 1 and 2 for gas, and Zone 21 and 22 for dust. For Zone 0, other methods such as intrinsic safety (Ex ia) or encapsulation (Ex ma) are required.
A: No. Type ‘p’ pressurization is not allowed as a sole protection method for Zone 0 (in gas) or Zone 20 (in dust). The standard covers Zone 1 and 2 for gas, and Zone 21 and 22 for dust. For Zone 0, other methods such as intrinsic safety (Ex ia) or encapsulation (Ex ma) are required.
Q: Is it necessary to monitor the flow of protective gas in a pressurized enclosure?
A: Yes, for all types (px, py, pz, pD) the standard requires either pressure or flow monitoring (or both) to ensure the pressurization is maintained. For enclosures that rely on a continuous flow of protective gas (e.g., using a fan or compressed air), a flow sensor is mandatory. If static overpressure is maintained without flow, only pressure monitoring is required, but any loss of pressure must initiate safe action.
A: Yes, for all types (px, py, pz, pD) the standard requires either pressure or flow monitoring (or both) to ensure the pressurization is maintained. For enclosures that rely on a continuous flow of protective gas (e.g., using a fan or compressed air), a flow sensor is mandatory. If static overpressure is maintained without flow, only pressure monitoring is required, but any loss of pressure must initiate safe action.
Q: Does the Canadian version differ significantly from the IEC version?
A: CAN CSA C22.2 No. 60079-2-16 is technically equivalent to IEC 60079-2:2016, but includes national modifications to align with the Canadian Electrical Code Part I and Canadian environmental conditions (e.g., cold temperature ratings, grounding practices). Manufacturers seeking CSA certification should obtain the CSA edition directly to account for these changes.
A: CAN CSA C22.2 No. 60079-2-16 is technically equivalent to IEC 60079-2:2016, but includes national modifications to align with the Canadian Electrical Code Part I and Canadian environmental conditions (e.g., cold temperature ratings, grounding practices). Manufacturers seeking CSA certification should obtain the CSA edition directly to account for these changes.
© 2026 CSA Group – This article is for informational purposes and does not replace the full standard. Always consult the official publication for formal compliance decisions.