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HVAC & Airflow

CO2 Ventilation Rate Calculator

Outdoor air needed to hold a CO2 target.

Enter your values

ⓘ Live results

Results
Per person airflow
18.3 CFM
Total outdoor air
457 CFM
In L/s per person
8.6
Steady CO2 at 15 CFM/person
1,127 ppm

Quick answer

Steady-state CO2 depends on the outdoor air per person; about 15 CFM per person holds roughly 1,000 ppm.

CFM per person = CO2 generation / (Ctarget - Coutdoor)

How to use the CO2 Ventilation Rate Calculator

  1. 1Set the CO2 target — 800 ppm for high cognitive performance, 1,000 ppm for general comfort.
  2. 2Enter outdoor CO2, typically 420 ppm today.
  3. 3Multiply by occupants and compare against your current outdoor air damper setting.

Worked example

Using the values the calculator loads with:

Inputs

  • Indoor CO2 target1000 ppm
  • Outdoor CO2420 ppm
  • Occupants25
  • ActivityLight office work

Results

  • Per person airflow18.3 CFM
  • Total outdoor air457 CFM
  • In L/s per person8.6
  • Steady CO2 at 15 CFM/person1,127 ppm

Frequently asked questions

Is CO2 itself harmful at 1,000 ppm?

Not directly, but it tracks other bio-effluents and studies link 1,000+ ppm to reduced decision-making scores.

How long to reach steady state?

Roughly three air changes, so 30-90 minutes in most rooms.

About this calculator

Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.