Canadian building code question

What are the NBC 2025 requirements for carbon dioxide (CO2) monitoring in Canada?

The NBC 2020 and anticipated NBC 2025 updates include requirements for carbon dioxide (CO2) monitoring as an indicator of indoor air quality, particularly in densely occupied spaces. CO2 monitoring requirements target occupancies where high occupancy density increases the risk of inadequate ventilation, such as classrooms, conference rooms, and assembly areas. The specific thresholds, sensor placement requirements, and alarm or indicator requirements depend on the occupancy type, ventilation strategy, and the edition of the NBC or provincial code adopted. CodeCan can retrieve the applicable CO2 monitoring provisions for your project.

CO2 monitoring emerged as a significant building code topic following the COVID-19 pandemic, which highlighted the importance of ventilation adequacy in occupied buildings. The NBC 2020 introduced CO2 monitoring requirements for certain occupancies, and the NBC 2025 is expected to expand or refine these provisions. For building owners, operators, and designers, understanding which spaces require CO2 monitors, where sensors must be placed, and what actions are required when CO2 thresholds are exceeded is increasingly important for code compliance.

What to check first

  • The NBC requires CO2 monitoring in certain densely occupied spaces as an indicator of ventilation adequacy, with requirements varying by occupancy type.
  • CO2 sensor placement, threshold levels (typically 1000–1500 ppm above outdoor concentration), and visual or audible indicator requirements are specified in NBC HVAC provisions.
  • Some provinces have adopted the NBC CO2 monitoring provisions while others are still in earlier editions — the applicable requirements depend on the code edition in force at permit.

Jurisdiction notes

National baseline

The NBC's HVAC provisions (Part 6) address indoor air quality and ventilation. CO2 monitoring requirements for densely occupied spaces were introduced in the 2020 NBC. The NBC references ASHRAE 62.1 for ventilation design, and CO2 monitoring is tied to demand-controlled ventilation (DCV) strategies.

British Columbia adoption check

The BC Building Code has its own adoption timeline for NBC 2020 provisions, including CO2 monitoring. BC has been proactive about indoor air quality requirements. Verify the current BCBC edition and any BC-specific amendments to NBC Part 6 ventilation requirements before specifying CO2 monitoring systems.

Project-specific variables

Occupancy type (classroom, office, assembly, gymnasium), room area and occupant load, ventilation strategy (constant volume vs. demand-controlled), building automation system capability, and the provincial code edition in force all determine whether and how CO2 monitoring applies to a specific space.

Work through it in this order

  1. Identify the occupancies in the building that may trigger CO2 monitoring requirements based on their density and ventilation strategy.
  2. Determine which edition of the NBC or provincial code is in force for your permit jurisdiction and whether CO2 monitoring provisions have been adopted.
  3. Review the NBC Part 6 HVAC provisions and any ASHRAE 62.1 references for CO2 sensor placement, threshold levels, and indicator requirements.
  4. Use CodeCan to query the CO2 monitoring requirements for your specific occupancy type, ventilation strategy, and provincial code edition.

Common questions

Which types of spaces require CO2 monitoring under the NBC?

The NBC targets densely occupied spaces where high occupant loads can elevate CO2 levels. Classrooms, conference rooms, assembly areas, and gymnasiums are commonly cited examples. The specific occupancy types and density thresholds that trigger CO2 monitoring requirements are defined in NBC Part 6 HVAC provisions.

What CO2 level triggers an alarm or indicator under the NBC?

The NBC specifies CO2 thresholds as concentrations above outdoor ambient levels (typically around 1000 ppm above outdoor) at which indicators or alarms must activate. The exact threshold depends on the code edition and occupancy. CodeCan can return the current threshold for your project's occupancy type.

Why doesn't this page give a definitive list of CO2 monitoring requirements?

CO2 monitoring requirements depend on occupancy type, ventilation strategy, room density, code edition, and province. The NBC 2025 provisions are also still being finalized and adopted by provinces on their own timelines. CodeCan takes your project context and returns the cited requirements that are actually in force.