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Understanding CSA C60079-13-19: Equipment Protection by Pressurized Room “p”
Comprehensive Guide to the Canadian Standard for Pressurized Enclosures in Hazardous Locations
Scope and Application
CSA C60079-13-19 is the Canadian adoption of IEC 60079-13:2017, which specifies requirements for the design, construction, testing, and marking of pressurized rooms used in explosive gas and combustible dust atmospheres. This protection technique, known as “protection by pressurized room ‘p’”, is intended to prevent the explosion of a flammable atmosphere inside a room by maintaining an overpressure of protective gas relative to the external hazardous area, and by controlling the atmosphere within the room to exclude flammable mixtures.
The standard applies to rooms that are pressurized with a protective gas (typically air or an inert gas) to prevent the ingress of a flammable atmosphere from outside. It covers both situations where the equipment inside the room is a potential source of release (internal sources) and where internal releases are negligible. The standard provides requirements for the pressurization system, monitoring, alarms, and shutdown logic to ensure that the protective function is maintained.
Tip: CSA C60079-13-19 is harmonized with the International Electrotechnical Commission (IEC) standard, but includes Canadian deviations for Class I and Class II hazardous location classifications. Always verify with the latest Canadian Electrical Code (CE Code) requirements.
Technical Requirements
Overpressure and Flow
The primary protective measure is the maintenance of a positive pressure within the room. The standard defines minimum overpressure values depending on the zone classification of the surrounding area. These values ensure that any leakage flow is outward, preventing the entry of flammable gas or dust.
| External Hazardous Area Classification | Minimum Overpressure (Pa) | Additional Flow Requirements |
|---|---|---|
| Zone 1 or Class I, Division 1 | 50 | Face velocity at any potential opening > 0.5 m/s |
| Zone 2 or Class I, Division 2 | 25 | Face velocity > 0.3 m/s |
| Zone 21, Zone 22, or Class II | 50 | Dust-specific filtration and flow |
The protective gas used must be either air with a flammable gas concentration not exceeding 25% of the lower flammable limit (LFL) or an inert gas. The pressurization system must be capable of maintaining the required overpressure under all normal operating conditions, including opening of doors or access panels, unless compensated by interlock systems.
Monitoring and Control Systems
To ensure continuous protection, CSA C60079-13-19 mandates monitoring of the pressure and, if necessary, the concentration of flammable gas inside the room. The standard outlines requirements for:
- Pressure monitoring devices: Capable of detecting loss of overpressure and initiating alarms and automatic shutdown of non-certified equipment if the pressure falls below a safe threshold.
- Gas detection: Required when internal sources of flammable gas may exceed 25% LFL. The detectors must be located strategically and interlocked with the pressurization system.
- Control logic: Must implement a time delay for shutdown to allow for a pre-purging cycle before energizing equipment, and to ensure that normal pressurization is established before power is applied.
Warning: Loss of pressurization, even temporarily, can compromise the safety of the pressurized room. The standard requires that any loss of overpressure for more than a predefined short time (typically less than 5 seconds) results in an alarm and, if not restored, automatic disconnection of power to non-intrinsically safe circuits.
Pre-Purging
The room must be purged with protective gas before energizing any electrical equipment that is not certified for the hazardous location. The standard requires that the purging process dilutes any residual flammable atmosphere to a concentration below 25% LFL. The purge volume is typically at least 5 times the room volume for gas atmospheres and may vary for dust. The effectiveness of purging must be verified.
Marking and Documentation
Pressurized rooms must have a permanent marking plate including the standard reference (CSA C60079-13-19), the type of protection symbol “p”, the protective gas used, maximum overpressure, and the intended external classification. The manufacturer must provide detailed documentation covering design calculations, pressurization system schematic, and instructions for installation, operation, and maintenance.
Implementation Highlights
Implementing CSA C60079-13-19 requires close cooperation between the designer of the pressurized room, the process engineers, and the electrical team. Key considerations include:
- Building integrity: The room must be constructed to withstand the overpressure and to limit leakage. All penetrations (cables, ducts, pipes) must be sealed.
- Pressure source reliability: The protective gas supply must be from a source that cannot be contaminated by flammable gas. Ducting from safe areas or dedicated compressors are common.
- Pressure relief: If the pressurized room has multiple compartments or large openings, the standard allows the use of pressure relief dampers to maintain overpressure during sudden pressure changes.
- Functional safety: The monitoring and control system should be designed considering the safety integrity level (SIL) requirements. While the standard itself does not mandate a specific SIL, it is recommended to apply IEC 61511 principles to the safety functions.
Best Practice: For new installations, consider implementing a comprehensive hazard and operability study (HAZOP) that specifically addresses loss of pressurization scenarios. This helps in defining the appropriate alarm setpoints, system response times, and manual override procedures.
Compliance and Certification
Compliance with CSA C60079-13-19 is typically required for electrical equipment installed in Canada that relies on the pressurized room protection technique. The certification is performed by accredited third-party organizations (e.g., CSA Group, UL, Intertek). The key steps in certification include:
- Type examination of the pressurization system design.
- Prototype testing of a representative room assembly (including worst-case leakage).
- Factory production control to ensure consistent quality.
- Field verification by the authority having jurisdiction (AHJ) after installation.
The standard also requires that the integrity of the pressurized room be maintained throughout its entire lifecycle. Periodic inspections and maintenance must be documented, and any modifications must be re-assessed for continued compliance.
Caution: Pressurized rooms that contain internal sources of flammable gas (e.g., gas analyzers, vent lines) introduce additional complexity. In such cases, CSA C60079-13-19 must be used in conjunction with parts of the IEC 60079 series dealing with gas detection and ventilation (e.g., IEC 60079-10-1, IEC 60079-17).
Frequently Asked Questions
Q: What is the difference between a pressurized room and a pressurized enclosure?
A: A pressurized enclosure typically refers to a smaller housing for individual equipment, covered by IEC 60079-2 (pressurized enclosure “p”). CSA C60079-13-19 deals specifically with rooms that are large enough for personnel to enter. The design principles are similar, but rooms require additional consideration for personnel safety and egress during pressurization loss.
A: A pressurized enclosure typically refers to a smaller housing for individual equipment, covered by IEC 60079-2 (pressurized enclosure “p”). CSA C60079-13-19 deals specifically with rooms that are large enough for personnel to enter. The design principles are similar, but rooms require additional consideration for personnel safety and egress during pressurization loss.
Q: When is gas detection mandatory inside a pressurized room?
A: Gas detection is mandatory if the equipment inside the room could release flammable gas into the room atmosphere in concentrations exceeding 25% of the LFL. If no such release is possible, gas detection is not required, but continuous pressure monitoring is still mandatory. For rooms with internal gas sources, a time delay for shutdown should allow for detection before escalation.
A: Gas detection is mandatory if the equipment inside the room could release flammable gas into the room atmosphere in concentrations exceeding 25% of the LFL. If no such release is possible, gas detection is not required, but continuous pressure monitoring is still mandatory. For rooms with internal gas sources, a time delay for shutdown should allow for detection before escalation.
Q: Can a pressurized room be used in a Class I, Division 1 location?
A: Yes. CSA C60079-13-19 covers both Division 1 and Division 2 locations (and their Zone equivalents). For Division 1, the overpressure requirement is higher (50 Pa minimum) and additional safeguards such as redundant pressure sensors and automatic shutdown are required. The standard also imposes stricter requirements on the pressurization system’s reliability for Division 1.
A: Yes. CSA C60079-13-19 covers both Division 1 and Division 2 locations (and their Zone equivalents). For Division 1, the overpressure requirement is higher (50 Pa minimum) and additional safeguards such as redundant pressure sensors and automatic shutdown are required. The standard also imposes stricter requirements on the pressurization system’s reliability for Division 1.
Q: Do I need to purge the room after a power outage?
A: Yes. Following any loss of pressurization (e.g., after a power outage or system shutdown), the room must undergo a pre-purging cycle before re-energizing non-certified electrical equipment. The purge duration should be based on a calculation using five air changes or a demonstration that the flammable concentration is below 25% LFL.
A: Yes. Following any loss of pressurization (e.g., after a power outage or system shutdown), the room must undergo a pre-purging cycle before re-energizing non-certified electrical equipment. The purge duration should be based on a calculation using five air changes or a demonstration that the flammable concentration is below 25% LFL.
Article prepared for technical professionals implementing explosive atmosphere safety solutions. Last updated: December 2026.