Home / Indoor CO₂ Steady-State Estimate Calculator

Indoor CO₂ Steady-State Estimate Calculator

Estimate a simplified indoor CO₂ excess concentration from generation and fresh-air flow. This tool uses co₂ generation (litres/hour), outdoor airflow (m³/hour) as its stated inputs. The output is reported in ppm above outdoors, so it should be compared only with figures in compatible units. Assumes steady state, well-mixed air and constant ventilation; not a health or compliance assessment.

How to use this calculator

  1. Measure or look up the input for co₂ generation (litres/hour) and check that its unit matches the field.
  2. Enter outdoor airflow (m³/hour). Change the supplied example numbers to match your own scenario.
  3. Read the calculation in ppm above outdoors and review the formula and limitations below before using it to make a decision.

How to calculate indoor co₂ steady-state estimate

Excess ppm ≈ CO₂ litres/hour ÷ outdoor airflow m³/hour × 1,000.

  • The formula uses the supplied measurements directly and returns its primary result in ppm above outdoors. No external data or background estimates are fetched by this calculator.
  • Use consistent reporting intervals and measurement units. A different unit or different definition for one input changes the meaning of the result.

Worked examples

Worked example: Indoor CO₂ Steady-State Estimate

Consider the following example input values: CO₂ generation (litres/hour) = 18, Outdoor airflow (m³/hour) = 60.

Apply the stated relationship: Excess ppm ≈ CO₂ litres/hour ÷ outdoor airflow m³/hour × 1,000.

Using those inputs gives approximately 300 ppm above outdoors.

Understanding the result

The result of the worked example is approximately 300 ppm above outdoors; it is an arithmetic outcome rather than a prediction of actual conditions.

Assumes steady state, well-mixed air and constant ventilation; not a health or compliance assessment.

Important notes

Assumes steady state, well-mixed air and constant ventilation; not a health or compliance assessment.

This result reflects the entered values only. Validate co₂ generation (litres/hour) against a relevant measurement or primary record; rounding, timing, or inconsistent units can affect practical decisions.

Frequently asked questions

What does the indoor co₂ steady-state estimate calculator measure?

Estimate a simplified indoor CO₂ excess concentration from generation and fresh-air flow.

What formula does this indoor co₂ steady-state estimate calculator use?

Excess ppm ≈ CO₂ litres/hour ÷ outdoor airflow m³/hour × 1,000. Assumes steady state, well-mixed air and constant ventilation; not a health or compliance assessment.

Can I rely on this indoor co₂ steady-state estimate calculator for a final decision?

First check the input units and whether the underlying assumption is appropriate. Assumes steady state, well-mixed air and constant ventilation; not a health or compliance assessment. For regulated or safety-critical decisions, verify with appropriate authoritative guidance.

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This page provides a calculation tool plus explanatory information so you can understand what the result means and when the underlying method may not fit your situation.