Indoor air quality issues in commercial buildings most often trace back to airflow distribution — not to filter media, not to the AHU alone, and not to the OA damper in isolation. A documented air balance under ASHRAE 111 is the right first step on most indoor air quality complaints.
How airflow distribution drives indoor air quality
First, indoor air quality depends on the system delivering design outdoor-air CFM to every occupied zone. Then, when a zone is starved of OA, CO2 climbs and complaints follow. Therefore, the balance has to land before equipment replacement is even on the table.
What a balance verifies on indoor air quality
Specifically, the balance verifies measured OA at every AHU, measured supply CFM at every diffuser, and damper position vs the BAS command. Additionally, the report ties any deficient zone back to a specific device.
When indoor air quality testing follows the balance
Furthermore, on occupant-complaint projects, IAQ testing typically follows the balance to confirm that CO2, VOC, and particulate concentrations drop into compliance with ASHRAE 62.1 once the airflow is corrected.
Standards context
ASHRAE 62.1 sets the minimum ventilation rates that buildings must deliver to occupied zones. LEED, WELL, and Fitwel layer additional verification on top — pollutant concentration limits, occupant-survey thresholds, and certification documentation. The relationship between ventilation rates, particulate filtration (MERV 13 or higher under most current specs), and humidity control (typically 30-60% RH) determines whether a building meets each standard. Properly distributed ventilation is the foundation; filtration and humidity round out the system. Source control — limiting VOC-emitting finishes, sealing combustion sources, managing moisture — closes the loop on what occupants actually breathe.
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