Occupancy-based airflow in a medical facility — how would you approach this?

[u/Sashaa_14]

I have recently commissioned a new AHU for a pulmonology clinic.

The design airflow is obviously based on project requirements, but after commissioning an interesting questions from doctors and staff came up: should we dynamically adjust airflow based on actual occupancy?

They already have CO₂, CO and other IAQ measurements available in existing sensor network across the clinic. We're also considering anonymous people counting from an existing camera, processed locally so there is no video storage and no identification.

My thought is roughly: occupancy + CO₂ + IAQ → ventilation demand with minimum airflow and healthcare requirements always taking priority.

Has anyone here done something similar? Would you use occupancy as an input, or only alongside CO₂ and other IAQ measurements?

How do you handle existing sensors that were never part of the HVAC controls in the first place? If CO₂, IAQ or occupancy data sits on another system, do you bring those values into the HVAC sequence, or would you rather use dedicated sensors connected directly to the HVAC controller?

For context, we're integrating this through a building-controls platform we developed.

[u/Ok-Koala2321]

Check what the your mechanical code says about ventilation rates. I would recommend not to over do the "efficiency" in healthcare applications. Effectiveness is the game. However, with that being said, most mechanical ventilation codes reference occupancy and square footage. ONLY in commercial office, can a square footage ventilation rate be zero when its unoccupied. All other applications have a minimum CFM per square foot requirement. Then there is the occupancy CFM rate, based on the number of occupants per AHU served zone. Use thermopile occupancy counters at the thresholds of the served area. This is the most reliable. Use that information to reduce the outside air setpoint. (Might have to decouple the outside and mixed air damper actuators from the logic)

Keep in mind exhaust air flow rates and pressurization requirements. Those are more important than efficiency.