Work out fresh air requirement instantly with clear inputs, formula shown and shareable results.
Fresh air demand scales with occupancy. Multiplying head count by the per-person rate gives total outdoor airflow, and dividing the sedentary carbon dioxide generation rate of about 0.0106 CFM per person by the ventilation rate per person predicts the steady-state indoor concentration above the outdoor baseline of roughly 420 ppm.
Fresh air
CFM = occupants x CFM per person; L/s = CFM x 0.4719
Steady-state CO₂
ppm = outdoor ppm + 10600 / (CFM per person)
CFM = occupants x CFM per person; L/s = CFM x 0.4719. Fresh air demand scales with occupancy.
It is the classic office rate that holds carbon dioxide near 1100 ppm, the level long used as a proxy for acceptable bio-effluent dilution.
This calculator takes 3 inputs: Occupants, Fresh air per person, Room volume. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.