AS 1668.2:2024 Ventilation Rates Reference Guide for Australian Commercial Buildings

What You Need to Know

AS 1668.2:2024 is the Australian Standard for mechanical ventilation in buildings. The National Construction Code calls it up as a Deemed-to-Satisfy pathway. If you design, build, or certify a mechanically ventilated commercial building in Australia, the rates in this standard set your minimum.

The 2024 edition replaces AS 1668.2:2012. It keeps the per-person and per-area framework but tightens prescriptive values and updates several occupancy classes. See our complete AS 1668.2:2024 update guide for the full list of changes.

This memo gives the headline rates engineers and contractors use most, the rules that govern demand-controlled ventilation (DCV), and the compliance traps we see most often on real projects. For the complete occupancy schedule, refer to AS 1668.2:2024 Table A1.

Occupancy class	Per-person rate	Notes
Office (open plan, private, meeting rooms)	10 L/s/person	Most common commercial rate
Retail (general)	10 L/s/person	Sales floor space
Entertainment (clubs, theatres, function rooms)	15 L/s/person	Higher rate for dense, mixed-use rooms
Classroom	10–12 L/s/person	Primary school typically at the higher end
Hotel guest rooms	10 L/s/person	Ensuite exhaust separate, 25 L/s minimum
Restaurant dining	10 L/s/person	Kitchen handled separately
Childcare (Class 9b)	12 L/s/person	Higher area-based floor often applies
Physiological floor (CO2 only)	2.5 L/s/person	DCV lower bound, not a design rate

Indicative reference based on industry-published values and CCC project use. Always confirm the exact figure in AS 1668.2:2024 Table A1 for your specific occupancy class.

Area-based floor for offices: outdoor air must never drop below 0.35 L/s per square metre of floor area, even with DCV active (AS 1668.2 Cl 3.3 reference).

For carparks, hospitals, kitchens, and laboratories, refer to the dedicated sections of AS 1668.2:2024. These spaces use different metrics (L/s per vehicle, ACHR, capture velocity) and are not on a per-person basis.

DCV uses CO₂ sensors to modulate outdoor airflow against actual occupancy. AS 1668.2 has allowed DCV since the 2012 edition. The 2024 edition retains this provision.

• The system must hold indoor CO₂ below the design threshold. NCC 2025 Table F6V1 sets 850 ppm averaged over 8 hours (NCC 2025, Table F6V1)
• The outdoor airflow must never drop below the area-based floor (0.35 L/s/m² for offices). DCV modulates between the area floor and the design peak (AS 1668.2, Cl 3.3)
• Equipment must be sized for the peak design occupancy. DCV reduces operating energy, not equipment size (standard engineering practice)
• NCC Section J now mandates DCV in high-occupancy spaces above defined outdoor airflow thresholds. Check Section J before deciding it is optional (NCC 2025, Section J)

• Ignoring the area-based floor. A lightly occupied office still needs the 0.35 L/s/m² minimum. Headcount-only DCV will undershoot.
• AHU sized to the DCV minimum, not the peak. The fan and coil must handle full occupancy. DCV only turns down the airflow.
• Borrowed ventilation specified without checking the source room. The source must meet its own rate first and have surplus available.
• Healthcare projects still using 6 ACHR for isolation rooms. Equipment and ductwork need re-sizing for 12 ACHR.
• Carparks designed to 2012 contaminant rates. The 2024 reductions cut both capital and operating cost on multi-level carparks.
• Outdoor air intake placed near loading docks, exhaust louvres, kitchens, or busy roads. Compliance values mean nothing if the air entering the building is contaminated.
• Documentation issued under one edition, certification required under another. Lock in the edition with the certifier at the start of the project.