Calculator
Example data
Example values show typical indoor air calculations. Adjust to match your space, sources, and ventilation.
| Scenario | V (m³) | ACH (1/h) | Cout (µg/m³) | G (mg/h) | kdep (1/h) | kdecay (1/h) | Qr (m³/h) | η | Mode |
|---|---|---|---|---|---|---|---|---|---|
| Office, moderate source | 240 | 1.5 | 12 | 180 | 0.15 | 0.05 | 900 | 0.6 | Transient (t=2 h, C0=5) |
| Home, low ventilation | 320 | 0.5 | 18 | 90 | 0.10 | 0.02 | 0 | 0 | Steady-state |
| Workshop, strong filtration | 150 | 2.0 | 10 | 400 | 0.25 | 0.08 | 1200 | 0.85 | Steady-state |
Formula used
This calculator applies the well-mixed single-zone mass balance model:
dC/dt = (Q/V)(Cout − C) + G/V − (kdep + kdecay + kfilt)·C
- C is indoor concentration (mass/volume).
- Q is outdoor air flow rate (volume/time).
- V is room volume (volume).
- G is indoor generation (mass/time).
- kdep and kdecay are first-order losses (1/time).
- kfilt = η·Qr/V represents recirculation filtration (1/time).
With constant inputs, the steady-state concentration is:
Css = (kvent·Cout + G/V) / λ, where λ = kvent + kdep + kdecay + kfilt and kvent = Q/V
The transient solution is:
C(t) = Css + (C0 − Css)·exp(−λ·t)
How to use this calculator
- Select transient for time-based prediction, or steady-state for long-run conditions.
- Enter the room volume and choose the correct unit.
- Choose ACH or an outdoor flow unit, then enter the value.
- Provide Cout and G in consistent concentration and mass units.
- Set loss terms: kdep, kdecay, and filtration via Qr and η.
- For transient mode, set C0 and t, then click Calculate.
- Use Download CSV or Download PDF to save the run.
Tip: If the space is not well-mixed, treat results as approximate and consider multi-zone modeling.